Hi Stuart,
The Live Control sliders for the volume of the keyboad parts Left/R1/R2/R3 (and the corresponding virtual volume sliders in the Mixer display) adjust the parameter "Volume ... (Offset)". This affects the "internal" volume of the Voice currently used in that Part.
As a test, please set the internal volume of the current Right1 Voice to 127 (in "Voice Edit > Common > Volume". Then the corresponding Live Control Slider should actually send the CC #7 values 0 - 127.
P.S.
It may also make a difference whether the Right1, Right2, Right3 and Left parts are used directly in the MIDI Setup > Transmit (such as in the MIDI template "All Parts"), or whether the special parts "Upper" and "Lower" are used (as in the MIDI template "KBD & STYLE"). The main difference is that in the first case the relevant keyboard parts must be switched on so that the MIDI data can be sent externally. When using "Upper" and "Lower", however, the MIDI data is ALWAYS sent on the two channels used, even if all keyboard parts are switched off.
Best regards,
Chris