Tp9s stiffer springs

Hi.
I’ve recently bought a nice and very portable Alesis Quadrasynth.
Cleaned it well. All good. I know it has Fatar Tp9s (i think semiweighted) with aftertouch. Common and well tested action.

But coming from a weighted (roland a 80 - kawai mp7) and good semiweighted (gem s2, yamaha dx7, korg m1) background, the board feels kind of light for controlling and playing it, as i want.

Is there a way to make the keys a bit harder?
Different harder- stiffer springs maybe?
I think the normal Tp8s and all tp7s and tp9s versions wear the same springs.

Thanks in advance