I dive double steel HP120s, and I love them. For tec, I dive them with a drysuit, a SS BP, an AL80 deco bottle and a AL40 deco bottle, + JetFins, canister light, reels, etc. In (cold) fresh water I found the Dive Rite Rec Wing at 51 lbs to be just a little light for the combined weight. I also found the dual bladder DR Super Wing, at 77 lbs, to be definite overkill. I ended up with a Halcyon Expolorer 55 and, as Goldilocks said, 'It is just right'.
I think anything less than 50 lbs would be inadequate as you move toward tec / cave. An AL BP may help, but why bother.