Keys seem harder when playing via Pianoteq

Hello,

I usually practice on my Roland FP-90 with its built-in SuperNATURAL sound engine. I used to find keys of Roland quite hard and stiff but over time I simply got used to play on it. I have just tried new Pianoteq 6 and its new Steinway & Sons piano models. Everything is great. I am very impressed with quality of sound but there is one thing I noticed. When I connect Pianoteq and try to play anything I have impression that keys become stiffer. I can't fully express this. It is like playing on different piano with much harder keys.

I thought at first it would be something to do with a delay introduced when you use software piano models. I fiddled with delay a little bit changing buffer size from 1024 samples down to 64. Somewhere between 512 and lower I could not recognise the delay at all. So I left the setting to 256. With 48kHz sampling frequency, 256 size gives something about 5 ms delay. I have not noticed much improvement, however. The keys still seem stiff.

Then I though it would be something related to Volume, I increased volume as well but still the impression is the same. Somehow, I noticed that ppp threshold is different - higher--I need to be slightly more firm to play ppp. Otherwise PT does not generate sound.  I also calibrated PT to get optimal velocity curve. It boosted middle part slightly and made velocity curve sort of concave. I had to reduced it as it caused sound to be more "metalic".

At this stage I don't know what else is to change. There are plenty of settings I don't know. I am thinking on Dynamics which increases or decreases range between quietest and loudest sounds.

Apart from that, does someone else have similar feeling when one compares playing using built-in and PT build sounds?

Thanks