Still my favourite of all the 531 routines. I'd stick to it for life if I could--but better follow Jim's advice and throw in some variety.
Anyway, if, to use the above example, your squat TM is 400lbs, then you increase the weight by 10lbs on the main 531 sets as per usual. The first month of BBB (at 50%) would then be 5x10 with 200lbs; second month would be 5x10 with 246lbs; third month would be 5x10 with 301lbs. My diet was all over the place and I managed to do it. At 6' 1" and weighing a Herculean 135lbs before I began weightlifting, believe me, with genetics like that, if I can do this anyone can. Just be careful with that TM and make sure it's on the money.