That's a pretty subtle curve. It's doubtful you'd even really notice it unless you've been playing Pianoteq with the RD-2000 using the default linear curve for a significant amount of time.
I developed the curve below for my RD-700NX based on getting Pianoteq's loudness (LUFS) response to match the response of the RD-700's onboard sounds which should be similar to the RD-2000. Specifically, I was matching Pianoteq's Steinway D Jazz Recording preset to the RD's Clear Studio preset with onboard reverb disabled in both and Limiting disabled in Pianoteq. I don't think the relative velocity response of either should vary greatly for different presets, but key to getting a matching loudness response with this velocity curve is raising the Dynamic Range of the Pianoteq preset to 53dB vs. the default which tends to be around 40dB.
You're probably not really used to the response of the RD-2000's onboard sounds, either, if you're new to it, but I'd be curious to hear how this feels to you with Pianoteq:
Velocity = [0, 4, 8, 12, 16, 20, 24, 32, 56, 104, 120, 124, 127; 0, 2, 12, 28, 38, 46, 51, 58, 75, 106, 113, 119, 127]