So I modded my Hori EX2. Amongst doing other things one of the things I did was replace the microswitches with Happ Cherries. However one thing I noticed is if I hit one direction ie forward and I let go of the stick, it’ll fly back and hit the opposite direction and set off the opposite direction -> backward. How do I fix this? A stiffer spring?
This is called deflection. It’s mainly a factor of engage distance (how far away the switches’ activation points are from neutral), spring strength, and weight of the shaft.
A lighter shaft (like the hollow ones used for balltop LEDs) helps reduce it, so would a stronger spring. I’m betting that the cherry switches give your stick a shorter engage distance than the switches you replaced.
Or you could just hold on to the stick instead of releasing it, like a lot of players do.
I was thinking of adding an LS-56 spring to the shaft. Would that help?
Yes, a spring of that strength would probably eliminate deflection completely.
I have the same problem too but I never bothered asking this… Also thanking for the tip on adding a stronger spring 
I haven’t been able to find a place to buy the spring and haven’t had time to check the hardware store. This is what I did to temporarily make it better. I took the spring out and pulled on it with my hands and stretched it out a tiny bit and then i put it back in. It’s gained back some of its stiffness. It will do for now