I haven't checked the maual, but assuming that there is no such setting, I'm curious, have you tried changing the velocity curve on the YC? On at least some Nords, changing the velocity curve for the internal keys also affects the velocity of incoming MIDI. (You can argue about whether or not it should work that way, but that's a whole other conversation.) If it happens that the YC does that, it could improve the response of your UF7. The tradeoff would be that it would also have the same "lower velocity" effect when playing the board's internal keys... but organ sounds don't use velocity; and if you're primarily playing your pianos from the external board, then you may not care much about altering their velocity repspnse from the internal keys; so then it will only be a factor on your "other" sounds that you may be playing from the YC's own keys, but you may find that their velocity response is still within your "acceptable" range even with the alternate velocity setting.

Otherwise, the answer could be to insert something lika a MIDI Solutions Velocity Converter between your UF7 MIDI Out and your YC MIDI in. Or connect the two boards via an iOS device, laptop, etc. and alter the velocity through an app.