Would it be wise to run the 5 x 5 BBB assistance template outlined in Beyond along side the 3/5/1 set up for main work from 5/3/1 for powerlifting? I would use the alternate-exercise BBB version (deads + BBB squats, etc.) Goal is strength (primarily on the main lifts), but any size gain would be welcomed.
And for the record, the reason I’m not just doing one of the assistance templates from 5/3/1 for powerlifting is I don’t have the book. Just have the original and Beyond. This seems like a good setup though.
Generally, no. The 3/5/1 version is set up to allow you to really push the final sets and hit heavy singles twice in one cycle instead of once with the original version (3’s week and 1’s week). Lots of extra reps on the final set and extra singles aren’t really recommended with boring but big.
I’ve been on some version of BBB for a little over 2 years now, and when I started combining the powerlifting template and joker sets with BBB (about 1.5 years in), what worked best for me in prepping for a meet was the 13 week challenge (and bench was the only lift that I actually did 3/5/1).
I tried to get an extra rep or two during the 3’s or 1’s week with squat and bench if I felt like it, only 1 (maaaaayyyybe two) joker set(s), then did the BBB work (two of the weeks were 5x5). I hardly ever did any extra with deadlift. If I did, it was usually during 1’s week, and it was never more than 3 total reps. I went for a heavy single (new 1RM if it was going GREAT) during the deload week and 3 light sets of 5-10. Week 13 was my meet, so I really only got through 12 weeks, but it turned out great - 6lb meet PR in the squat, 6lb lifetime PR on the bench, and 14lb lifetime PR in the deadlift (this meet and the most previous meet were only 14 weeks apart).
Alllllllllll that being said. It has taken me 8 years of training (and 2 consistently with 5/3/1) to figure this out for myself. If this if your first (or even 2nd or 3rd) time through a BBB template…PLEASE just do the required reps and sets, then move on to the BBB sets.