Well, i did my homeworks and here is what fits to me :

- with RD700SX Keytouch at MEDIUM (defaut parameter):
Pianoteq with a sin²x response ->
velocity = [0, 32, 64, 96, 127; 0, 11, 42, 84, 127]

- but i like also, to get a larger timbral dynamic, to keep Pianoteq normal velocity and to choose a HEAVY Keytouch on my RD700SX (or something between MEDIUM and HEAVY), and then to tweak the mezzo and forte hammer hardness.

XB

Even when pressing very lightly and slowly, RD-700SX still generates MIDI velocity of 1 and one could be tempted to shift the lower end of the velocity curve to the right with one step:

Velocity = [1, 127; 0, 127]

however with that setting the instrument is behaving strangely and producing silence when expected to produce sound, that's why I am not recommending it at all. (The test is conducted while playing Chopin).

To summarize: use factory defaults of Pianoteq and RD-700SX in order to obtain the optimal dynamic response.