I bought this disk on the recommendation of John Connoly of Aircooled.net. Here's the link -->
http://aircooled.net/new-bin/viewproduc ... 01&cartid=I opted for the sprung center variety (which they don't show for some reason) to try and reduce driveline shock a little, every bit counts.
The disk is a dual compound disk with a fiber material on one side and sintered copper "pucks" on the other, it's designed to slip a little and then stay put. This is really important on the type 1 transmission which was designed for ~ 50 hp, that little bit of slippage greatly reduces the shock load in the tranny and helps save it from gernading. John runs this disk in his 250 hp race car. I haven't done any "drag style" launches with it yet (my new engine and tranny literally have about a mile on them, lol) but I can say for sure that sucker grabs HARD! Especially going from a stock disk. I am using it with a Kennedy Stage 1 pressure plate (1700 lb). This combo feels really nice, it grabs very hard, but after a few take-offs you get used to it and you can engage it very smoothly. I give it an A+ so far, I'll update my impressions of it when I get some more time on it.