Think I agree with JOEBOB69 here.
I personally don't think of calling 55 on the button against a CO opener as setming per se. He's probably opening a wide range that won't necessarily stack off when we hit our set, unless he is very bad, or very unlucky (hits 2P), or actually has us beat. So here there will be other factors in play, like do I think the SB or BB will call, giving me more implied
odds. Do I think I can take it away from the CO on the flop or turn? Point being, imo, you can't profitably setmine here, you have to have a bigger plan than fit or folding the flop.
Against a tight UTG opener and an MP caller, if I'm on the button with 55 I am ABSOLUTELY setmining. I hit the flop or I fold to a cbet. Sometimes if it goes check check I'll stab depending on the villains and board. If I suspect the villain is check calling, I'll check behind (obviously). If UTG is weak tight (fit or folding) then I'll defo stab, as MP would have done by the time it gets to me if he has anything, for example, a pair of balls
OOP, similar to the second scenario, I will call in the SB or BB with a tight UTG opener and MP caller, but only this time I have to wait until the turn card to stab at it, which is a little more risky. If the UTG opener is loose and MP called, I could even find a 3bet or fold OOP with 55.