The throw is 22 degrees to one direction. My WinWing F16EX grip weighs maybe 1 kg. That is 10 N. The height of the joystick might be something like 0,2 m from the gimbal center - depending heavily on the extension of course. Therefore, with this grip and total throw we can calculate the momentum of the grip to the gimbal. With 22 degrees and 0,2 m height you get 0,075 m of travel on at the bottom of triangle. That means the momentum is 0,075 m * 10 N = 0,75 Nm.
If we were to add Z-extension that brings the joystick 0,1 meters towards you that will change the calculation. It not going to be exactly 0,1 meters more momentum but precision is good enough for usage. So we would get 0,175 m * 10 Nm = 1,75 Nm momentum from the grip with the Z-extension. So roughly 1 Nm of required compensation for the Z-extension.
Of course this doesn't include the weight of the extension. However, most of the momentum comes from the grip because it weighs more and is further from the center.
With a weight put on the pulley the force could be counteracted. If the weight is attached outside the belt - say 0,06 meters from the center of gimbal. 1 Nm / 0,06 m = 16,7 N --> 1,7 kg. Thats quite a heavy weight. The bearing shouldn't be a problem but I wonder how problematic it would be for the motors. Nevertheless, the maximum throw is probably not the best way to compensate the extension if we consider a solid weight. Additionally, less weight is required when stick is centered.
A spring attached to the cog might be better option since the force required increases as the spring is loaded. This would put lesser force when the stick is centered and more force when stick is pulled, which is ideal
