Ok, so this calling a 4bet IP thing is super complicated, so I'll do my best to just give you guys some things to think about. And I have taken some info from Galfond's vid on BFP fwiw.
So there's basically two types of hands that we may want to consider calling a small 4bet w/ 100bbs IP, and for this example we'll use A8s and 75s. And we'll assume we 3bet to 36, villain 4bets to 82..so we need 27% equity to breakeven on the call.
So our hands have the following equities vs various ranges:
A8s has 30% equity vs TT+, AKs, AKo
A8s has 37% equity vs TT+,AKs,AKo, 98s, 87s, 76s
75s has 27% equity vs TT+,AKs,AKo
75s has 30% equity vs TT+,AKs,AKo,98s,K4s,A4s
So clearly for these to be unprofitable calls, we must be at a disadvantage postflop. Galfond believes that we are NOT at a postflop disadvantage vs some avg/weak opponents. And that we may be at an advantage w/ a hand like 75s because of our perceived strong range, and the fact that this can create very good deceptive postflop situations.
Let's look at some flops w/ our two hands vs the uber tight 4betting range. So w/ A8s (these flops assume we have a backdoor FD) we have the following equities vs TT+,AKs,AKo:
70% on A53r
59% on AT3r
42% on J83r
20% on 763r
Another thing to consider is that when we have A8s, villain will flop less than TP about 50% of the time w/ TT+, AK. So when we have a hand like 75s, there should be a lot of good bluffing opportunities since a lot of flops won't be good for our opponents range.
Now let's look at a couple flops w/ 75s (again assuming we have a BDFD).
75s vs TT+,AK
42% on J73r
29% on 983r
These can be good situations particularly if our opponent is likely to be cbetting small (extremely common in 4bet pots), and will be likely to give up on bluffs and/or be turning his hand faceup on later streets.
Now I'm obv not saying "don't ever fold to 4bets IP!" I just wanted to provide you guys w/ some things to think about. And I suspect that some of these numbers may be pretty surprising to you wrt how much equity we may have..esp keeping in mind that we assumed basically the tightest 4bet range possible for villain in most situations.
So gl, and thanks for all the feedback..please keep it coming