Leonardo asks "What force (G) may be deemed necessary to prevent pilot to move his arm at all ?" That depends on the pilot and the layout of the stick. Fighter pilots manage through 9 G somehow.
On the other paw, however, consider holding a very full drink in one hand as you go over a speed bump a little too fast. Now imagine that in turbulence from a CB in three dimensions as you try to reach for the stick. The sidestick has a nice physical layout to ensure stability in turbulence. But you have to get there first and you have to be pretty tightly belted in to keep it stable, I'd bet.
I guess another way to look at it is to imagine you have some springs attached to your wrist exerting 3G accelerations (maybe 10 to 30 pounds force) in random directions every couple seconds as you try to put your hand onto a joystick attached to the arm of your chair. Of course, you desperately don't want to HIT that joystick knocking it full over by accident. Might even 1 G of such acceleration be enough to make it hard to get on the stick accurately and in a hurry?
JD-EE