I had 8" ptc in my last 9000rpm sb w2 engine which worked great.
Now with my new R5 engine i bought 7" converter because lack of torque and ordered with 7200 stall speed. It came with 8600stall and didnt quite was what i expected. So it got tightened and now it is 7500stall. That worked great for 3 runs and then my speed came down every run. It took less than 10 runs and now its good for trash can. It heats the oil super fast and car is atleast 0.5s slower than before.

I dont know what broke in it. Stall is still the same but it doesnt run as good as it was. Maybe sprag failure? Transmission was also checked and it works ok. PTC converter should take 800+ hp without problems more than 10 runs?