I am not sure if this helps you at all; but I just put a spec twin disk in my car, and the straps are completely diffrent on my PP to yours.. Your cluch only has three straps in each location, where mine has four. In addition your straps look longer, thinner, and narrower than the straps on my PP. The straps on my PP are made of a thick black colored steel, and are about just over an inch wide. When I assembled the clutch I compared them to the straps on the old RPS Carbon/Carbon and my ACT PP and was impressed with how thick, wide, and short they were. I was talking to Justin Nenni the other day and ask about this spec twin disk, he said tuned a car that put down right at 1100 rwhp with the twin disk.
It looks like the single disk PP is using straps similar to the RPS/ACT/Stock PP; in fact is it a reworked stock PP? Can you take a picture of the top of the PP? If it is a re-worked stock it is likely the same problem that hit the RPS re-worked stock PP's. My guess is that the Toyota stock PP straps are not as strong as they used to be. I would however push back on Spec.. obviously this was pure and simple a failure that should not have happened.
I know these are not the best pics of the twin disk clutch, but it is all I have handy. As you can see the twin disk unit is all billit.. It looks like a really nice clutch over all.
Keep us informed!
Spec's twin disk clutches are a high power for moderate cost solution we have all been looking for in Supras.. I hope thier customer service does not fall short of the mark.