I posted this on another forum, but thought it'll be relevant here also. Hope that is ok.
I didn't like how the stock spring sits a little crooked on the pressure plate and since the Strobe Sprong isn't made anymore, I made my own. Best of all, it is made from 'bonnet packing' available in the plumbing section at Lowes or HD for 2 @ $.79.
I used a #8 nut to help center the rubber ring. It is just the right size to fit over the input shaft and fit inside the rubber ring.
I used an extra slipper pressure plate turned around. The tapered shape of the pressure plates also helps center the rubber ring. I also tried it with a fender washer and it works fine too. It's just harder to center.

I'm using a strobe slipper, but it should work just the same with the stock slipper. I don't think the inner nut is totally necessary, but it does help keep everything centered . I'm running it about 1/4 to 1/2 turn out from locked and it seems to work pretty well on a 8xl emaxx.