Korg SP-170: going mad about the curve velocity

Hi everybody,

I'll be some month far from (both) home(s) and so I rented a cheap SP-170 to keep my fingers occupied. At the same time, I discovered that in the campus I'm in there are some awesome free music rooms with some uprights and 4 grands (a Kawai, a Yamaha, a third whose brand I forgot, and a nice Blüthner) so I quite often do to and fro from my room to the music rooms, and I kind of have the feeling of a grand piano action in my hands.

Compared to this, the action of the SP-170 does a quite poor job, but that's nothing worse than one would expect from an entry-level piano (I might even say that, for being such a cheap piano, it does quite a good job).

What I couldn't expect, though, is that I'm having some trouble with dynamics as well, and who says dynamics says velocity curves.
I keep changing them, and never finding a satisfactory one.

First I tried with the one on the PTQ's site library :
Velocity = [0, 25, 41, 54, 69, 82, 98, 127; 6, 15, 35, 57, 94, 116, 123, 127]
But I found impossible to play pianissimo and the piano are still too loud.

I then tweaked it a little bit, and I had that :
Velocity = [11, 25, 36, 43, 52, 65, 77, 95, 110, 127; 0, 8, 10, 22, 38, 61, 88, 112, 121, 127]
Which is more reasonable, but rather hard and quite steep when going to mp to f. It's somewhat similar to the Kawai's touch in the extremes, but not nearly so smooth in the middle-ranged velocities.

Then, I reverted to a "normal keyboard" standard velocity, which I find ok and really similar to the Yamaha C3's touch. The problem is - I don't like the C3's touch that much, I find it somewhat too light.

Eventually, I tried to calibrate the keyboard with the calibration tool, and the results gave me a curve with is realistic enough in its progression, but ridiculously light :
Velocity = [0, 1, 23, 56, 77, 126, 127; 0, 0, 32, 64, 96, 127, 127]

I still can't decide which curve I should use, I keep switching between those four options without finding one that is completely satisfactory to me... anyone having the same problem ?