Live $1/$2 NL. Full table. Literally just sat down like five hands ago.
Hero = $300
V1 = ~$100. Male, white, 70s. Unknown.
V2 = ~$300. Male, white, 20s with hat/shades/headphones. Appears to be a thinking opponent. I've seen him open-raise two hands preflop already, and both times won a small pot postflop.
V3 = ~$100. Male, white, 60s. Unknown.
(there were other stacks more like mine around the table, I just happen to be dancing with a few of the short ones for this particular hand)

UTG (V1) raises to $7. Folds to UTG+2 (V2) who calls. I raise to $30 from MP with KK. Folded to Btn (V3) who calls. V1 calls. V2 calls.

Flop: 8 7 2
V1 shoves all-in. V2 thinks for about 20 seconds. We look at each other for a few seconds, but I am not getting a read on him. He calls ~$70.

I am suspicious that he has flopped a set on me...
1) Hero decision? I mean, V1 and V3 I'm shoving all day. But V2....given the SPRs and given your read on him, how are you handling this situation?

V2's range to call here has to be sets and overpairs, yeah? There shouldn't be any TP or draws in his range to call pre. If he's actually good, sets need to be discounted too, as he's getting an iffy price to set-mine pre. His range to flat twice pre is prob something like 77-JJ.

I flat, and likely fold if he makes any significant bets into the dry sidepot. I seriously doubt he'd do that as a bluff, esp as he has no reason to believe you'd fold a big overpair to it. I suspect his overpair range checks it down, and you might even consider a small v-bet on the river if he checks twice. His set range may check turn, hoping you'll spazz, but will rarely check twice.

~1 year or so ago, I read the Professional Hold'Em book by Sunni Metha/Miller etc. The concept of SPR/commitment is quite useful....except I think I'm misusing it. Perhaps you can guide me and help me re-wire my brain. For example, in the case of this hand, I did not consider flatting to be an option. From my POV, I'm either committing on the flop (shove) or deciding I'm behind (fold). But you are saying you are comfortable flatting here. Are we not creating a pot too big to get away from if we call the flop?

I think you can actually make a pretty easy fold on a later street after calling due to the all-in player and the fact that your hand is fairly well-defined by the turn, and his is either a set or an overpair. I'd call, check behind the turn, and then try to value bet the river if checked to, maybe calling a small / medium bet and folding to a big one.

As a well known coach ITF said, "SPR is not Ed Miller's permission to turn off your brain." In general, I agree that putting in 1/3 of your stack in and then folding is bad, but this is a special circumstance, not a simple HU pot. Main pot is protected and side pot is dry. Very different circumstance.