Solid thoughts in your post for sure and now a naive question

I think we can assume the average cold 4-bet range is underbluffing in
your pool (assumptive, but I think most players would feel
uncomfortable bluffing in that spot at all). If that's the case,
perhaps ignoring the loose'ish opener and figuring out a proper 4B
range HU vs the 3-bettor would be a good model.

When you said model you are talking find equilibrium using a solver or just build a range to take advantage of the likely FE we have preflop? Not sure because Villain might flat with some hands so I don't know how much useful could be a preflop model

Ty in advance

You can use a pre flop Nash solver (limited to HU scenarios) and make a crude model of ignoring BB (rather safe) and the opener (weakest assumption in the model) and calculate a cold 4-betting range HU vs the 3-bettor. You'd have to make an assumption about the 3-bettor's range.

Or you can use a pseudo-Nash (as in, Nash for pre flop jam/fold spots but does not take future post flop play into account when there is money left to play for) solver like HoldemResources Calculator, make assumptions about opener's and 3-bettor's ranges and you'll get a 4B range using the check down model (when you get called, there is no betting post flop). What this model would tell you is what is sound to stack off with, and what would be a reasonable bluffing frequency.

Since it uses the check down approximation, this model will overvalue raw pre flop equity, but it should give you a pretty good idea about stack off range and how much you should bluff. And it does recognise the presence of the BB and the opener.

I'd use the 2nd approach and make a quick and dirty model with HRC to see what is reasonable to do.

^^ Ty a lot, gonna take a look at HoldemResource Calculator first

I think we can assume the average cold 4-bet range is underbluffing in
your pool

Just to know, I made a population study, they 4bet wider than I thought (pure value made by QQ+,AK). Probably, some short stack influenced the results, maybe I should filter even more, anyway...
DB: 1,2 M hands
Spot: UTG raises, MP 3bets, Someone else has to decide, No hero stats (total instaces: 13640)

Filtering down more to exclude most random fishes (at least 10 opportunities to do something against UTG raiser and MP 3bettor) I got

The 4bet % is the same, probably fishes call wide, so that's wide there's a difference between call % and fold %

Aggroshooter:

Those are surprising numbers. Regular tables?

Yep regular tables.
Did you expect other frequencies? it isn't a .com site, it is a segregated pool

Definitely expected other frequencies. A cold 4-bet range of > 4% vs UTG open + MP 3B sounds more like a reasonable MP 3-bet range vs UTG with 4 players left to act (when MP also has a flatting range, which ties up a lot of his linear hands and limits how wide he can 3B).

For reference, when BB finds himself heads-up with a 16-17% UTG opener, the Nash solution is to 3B around 5.5% (Pio pre flop sims). Nash pre flop ranges are rather loose-aggressive (for example, 21% 3B for BB vs 45% SB open), so it's strange to see a micro pool cold 4B close to what a Nash BB player would 3B.

Are you sure you filtered away UTG's 4-bets and got only the ones from players who have not yet acted?

Definitely expected other frequencies. A cold 4-bet range of > 4% vs
UTG open + MP 3B sounds more like a reasonable MP 3-bet range vs UTG
with 4 players left to act (when MP also has a flatting range, which
ties up a lot of his linear hands and limits how wide he can 3B).

Just to make sure I'm getting it right, the pool is cold 4betting wider? I mean, if you expect a MP 3bet range of 4% vs UTG, a someone else 4bet range should be even lower...

Are you sure you filtered away UTG's 4-bets and got only the ones from
players who have not yet acted?

I have to double check, maybe UTG 4bets are included when a player cold calls, I'm going to check it out and update you

Just to clear up any confusion, I expected the cold 4B% to be tighter. :-)

Just to clear up any confusion, I expected the cold 4B% to be tighter.
:-)

ty

Are you sure you filtered away UTG's 4-bets and got only the ones from
players who have not yet acted?

Double checked and tweaked the filter in order to exclude completely UTG's 4bet, my filter is showing hands where:
; UTG raises, MP 3bets
; UTG VPIP, MP VPIP, UTG NOT VPIP (when all folds to)
; UTG raises, MP 3bets, UTG doesn't 4bet ever

3.5% is more reasonable, but do these numbers say that the players behind are calling MP's 3-bets cold 15% of the time? Or am I misunderstanding something? :-)

What is the MP 3B%, since we're at it?

3.5% is more reasonable, but do these numbers say that the players behind are calling MP's 3-bets cold 15% of the time?

That value include all calls, and for instance, if BTN calls and UTG calls, it would be count

The number below instead is only showing when UTG opens, MP 3bets and CO or BTN or SB or BB calls

What is the MP 3B%, since we're at it?

Since I'm fearing monster under the bed, I would be more inclined to raise because when the flop is XXXss I hate life, but this way of thinking shows how behind I am.
I also think, in general, if one of those have a hand, they can't find a fold, at least pre. So my 4bet would be for pure value.
I think in order to get a better understanding of the spot, specifically vs my pool, I should perform a population study, later on I post the results for my DB (which have 1,2M on Hero)

Pool stats (1,2M hands):
Spot: UTG opens, MP 3bets, Someone 4Bets, No Hero Stats (total instances 1930)
Stat below shows UTG and MP combined frequecies