I was playing Pac-Man on crack mode (speedup cheat) last night, and my wrist got all cramped after a couple screens. So I took the E-stick apart (my dedicated 4-way since it does diagonal games too) and pulled out the spring for the shaft and found it to be too stiff. I started to wonder if it could be replaced with something softer...
Tonight I went to Home Depot and found a spring of the same approximate size, but made of a thinner gauge wire. Popped it in the E-stick, and now it feels just like a Happ super (but with a shorter throw.)
The spring was a "Handyman Springs" brand (Prime-Line Slide-Co), part# SP-9706. The specs are 1/2" x 1-1/2" x .041