The BEST and REAL way to check your stall is data log.
Nail it from a high idle (1000 rpm) without tire spin and see where it flashes to or rolls over.
The brake stuff only checks yours brakes...really.
Post up your data or I'll subscribe to this thread and post up mine and help you check this out.
BTW...my rig is NOT a good example for you because I built my converter to flash at 3000, exactly where I launch at with my tranny brake and 2 step.....NO FLASH. My twin turbos make the power to "pull through" without stall.
Not great for the normal rig.
Just give me the data and I'll help.
With this thread I'll show you how to read the data log of your power and converter.
To start, an "off the shelf" converter or buying your buddies converter is NOT the way to go.
So many variables....a converter NEEDS to be built to match your combination. Yep NEEDS.