diff --git a/lib/logitech_receiver/settings.py b/lib/logitech_receiver/settings.py
index bdcb96c2..41ef9b6b 100644
--- a/lib/logitech_receiver/settings.py
+++ b/lib/logitech_receiver/settings.py
@@ -602,16 +602,22 @@ class FeatureRWMap(FeatureRW):
 
 
 class BooleanValidator:
-    __slots__ = ('true_value', 'false_value', 'read_offset', 'mask', 'needs_current_value')
+    __slots__ = ('true_value', 'false_value', 'read_skip_byte_count', 'write_prefix_bytes', 'mask', 'needs_current_value')
 
     kind = KIND.toggle
     default_true = 0x01
     default_false = 0x00
     # mask specifies all the affected bits in the value
     default_mask = 0xFF
-    default_read_offset = 0
 
-    def __init__(self, true_value=default_true, false_value=default_false, mask=default_mask, read_offset=default_read_offset):
+    def __init__(
+        self,
+        true_value=default_true,
+        false_value=default_false,
+        mask=default_mask,
+        read_skip_byte_count=0,
+        write_prefix_bytes=b''
+    ):
         if isinstance(true_value, int):
             assert isinstance(false_value, int)
             if mask is None:
@@ -645,10 +651,11 @@ class BooleanValidator:
         self.true_value = true_value
         self.false_value = false_value
         self.mask = mask
-        self.read_offset = read_offset
+        self.read_skip_byte_count = read_skip_byte_count
+        self.write_prefix_bytes = write_prefix_bytes
 
     def validate_read(self, reply_bytes):
-        reply_bytes = reply_bytes[self.read_offset:]
+        reply_bytes = reply_bytes[self.read_skip_byte_count:]
         if isinstance(self.mask, int):
             reply_value = ord(reply_bytes[:1]) & self.mask
             if _log.isEnabledFor(_DEBUG):
@@ -711,7 +718,7 @@ class BooleanValidator:
         if _log.isEnabledFor(_DEBUG):
             _log.debug('BooleanValidator: prepare_write(%s, %s) => %r', new_value, current_value, to_write)
 
-        return to_write
+        return self.write_prefix_bytes + to_write
 
 
 class BitFieldValidator:
@@ -837,7 +844,7 @@ class ChoicesValidator:
     :param choices: a list of NamedInts
     :param byte_count: the size of the derived byte sequence. If None, it
     will be calculated from the choices."""
-    def __init__(self, choices, byte_count=None, read_skip_byte_count=None, write_prefix_bytes=b''):
+    def __init__(self, choices, byte_count=None, read_skip_byte_count=0, write_prefix_bytes=b''):
         assert choices is not None
         assert isinstance(choices, _NamedInts)
         assert len(choices) > 1
@@ -850,7 +857,7 @@ class ChoicesValidator:
             assert self._byte_count <= byte_count
             self._byte_count = byte_count
         assert self._byte_count < 8
-        self._read_skip_byte_count = read_skip_byte_count if read_skip_byte_count else 0
+        self._read_skip_byte_count = read_skip_byte_count
         self._write_prefix_bytes = write_prefix_bytes if write_prefix_bytes else b''
         assert self._byte_count + self._read_skip_byte_count <= 14
         assert self._byte_count + len(self._write_prefix_bytes) <= 14
@@ -916,7 +923,7 @@ class ChoicesMapValidator(ChoicesValidator):
         self.choices = choices_map
         self.needs_current_value = False
         self.extra_default = extra_default
-        self._read_skip_byte_count = read_skip_byte_count if read_skip_byte_count else 0
+        self._read_skip_byte_count = read_skip_byte_count
         self._write_prefix_bytes = write_prefix_bytes if write_prefix_bytes else b''
         self.activate = activate
         self.mask = mask
@@ -1091,10 +1098,8 @@ class ActionSettingRW:
                             self.pressed = False
                             self.release_action()
                         else:
-                            print(self.key.key, cids)
                             for key in cids:
                                 if key and not key == self.key.key:  # some other diverted key pressed
-                                    print(key, self.key, cids)
                                     self.key_action(key)
                 elif n.address == 0x10:
                     if self.pressed:
diff --git a/lib/logitech_receiver/settings_templates.py b/lib/logitech_receiver/settings_templates.py
index 5e64c823..81a405d5 100644
--- a/lib/logitech_receiver/settings_templates.py
+++ b/lib/logitech_receiver/settings_templates.py
@@ -224,13 +224,17 @@ _DISABLE_KEYS_LABEL_SUB = _('Disables the %s key.')
 # _FeatureRW is for feature-based settings and takes the feature name as positional argument plus the following:
 #   read_fnid is the feature function (times 16) to read the value (default 0x00),
 #   write_fnid is the feature function (times 16) to write the value (default 0x10),
+#   prefix is a prefix to add to the data being written and the read request (default b''), used for features
+#     that provide and set multiple settings (e.g., to read and write function key inversion for current host)
 #   no_reply is whether to wait for a reply (default false) (USE WITH EXTREME CAUTION).
 #
 # There are three simple validators - _BooleanV, _RangeV, and _ChoicesV
-# _BooleanV is for boolean values.  It takes three keyword arguments that can be integers or byte strings:
-#   true_value is the raw value for true (default 0x01),
-#   false_value is the raw value for false (default 0x00),
-#   mask is used to keep only some bits from a sequence of bits.
+# _BooleanV is for boolean values.  It takes five keyword arguments
+#   true_value is the raw value for true (default 0x01), this can be an integer or a byte string,
+#   false_value is the raw value for false (default 0x00), this can be an integer or a byte string,
+#   mask is used to keep only some bits from a sequence of bits, this can be an integer or a byte string,
+#   read_skip_byte_count is the number of bytes to ignore at the beginning of the read value (default 0),
+#   write_prefix_bytes is a byte string to write before the value (default empty).
 # _RangeV is for an integer in a range.  It takes three keyword arguments:
 #   min_value is the minimum value for the setting,
 #   max_value is the maximum value for the setting,
@@ -238,8 +242,8 @@ _DISABLE_KEYS_LABEL_SUB = _('Disables the %s key.')
 # _ChoicesV is for symbolic choices.  It takes one positional and three keyword arguments:
 #   the positional argument is a list of named integers that are the valid choices,
 #   byte_count is the number of bytes for the integer (default size of largest choice integer),
-#   read_skip_byte_count is the number of bytes to ignore at the beginning of the read value (default 0),
-#   write_prefix_bytes is a byte string to write before the value (default empty).
+#   read_skip_byte_count is as for _BooleanV,
+#   write_prefix_bytes is as for _BooleanV.
 #
 # The _Settings class is for settings that are maps from keys to values.
 # The _BitFieldSetting class is for settings that have multiple boolean values packed into a bit field.
@@ -292,7 +296,7 @@ def _feature_new_fn_swap():
 # ignore the capabilities part of the feature - all devices should be able to swap Fn state
 # just use the current host (first byte = 0xFF) part of the feature to read and set the Fn state
 def _feature_k375s_fn_swap():
-    validator = _BooleanV(true_value=b'\x01', false_value=b'\x00', read_offset=1)
+    validator = _BooleanV(true_value=b'\x01', false_value=b'\x00', read_skip_byte_count=1)
     return _Setting(_FN_SWAP, _FeatureRW(_F.K375S_FN_INVERSION, prefix=b'\xFF'), validator, device_kind=(_DK.keyboard, ))
 
 
@@ -480,7 +484,7 @@ def _feature_speed_change():
             keys = [_NamedInt(0, _('Off')), key.key]
             return _ChoicesV(_NamedInts.list(keys), byte_count=2)
 
-    rw = _SpeedChangeRW('speed change', _DIVERT_KEYS[0]),
+    rw = _SpeedChangeRW('speed change', _DIVERT_KEYS[0])
     return _Setting(_SPEED_CHANGE, rw, callback=callback, device_kind=(_DK.mouse, _DK.trackball))