There is no magic number. Tuning is critical, battery voltage must be at least 12.6V. Surge in a high powered stereo will drop voltage to the trans and if it happens a the wrong time; you lose. Breaking traction during a shift with converter locked can break something. A slow action in the TCM because of ( whatever ) can break something.
Things like this is what a great builder takes into account and builds the trans accordingly. Knowing there are things we cannot control and some of the stupid things the truck owner will do; we have to modify and strengthen things as best we can. Even then, there is no guarantee something wont get hurt.
Now; Evan wants nothing to do with you so find another builder you trust and stop whining.