Stop and go is defined (I guess) as just calling pre, leaving SPR < 1 behind for the flop. We then commit with flopped equity and otherwise fold. So, no donk-shoving every flop.
I just want to calculate/estimate showdown equity (to which we could later add fold equity, if available)

Side note: A similar thing often occurs in PLO, when calling a 4bet (expected to be AAxx) to see a flop and commit on favorable flops. (I read an article once that at SPR=1 this play favors the caller even with a wide range)

Real world example:
BU raises, we 3bet in the BB, BU now min-4bets.
We are pretty sure that he has exactly AA.
Pot odds are 20%-25%.
Calculation for setmining is pretty easy. We flop it 12.5% of times, so we need to win one more potsized bet to break even.

But what about a hand like KQs/JTs?
We need a pretty advanced calculation to account for the different types of flops we commit on, etc.
Flopzilla shows those percentages, but fails to put it all together as equity vs AA (or range)

Any easier, more convenient way to go about this?

overbet the flop

Technically a stop-n-go inolves calling a raise and open shoving the flop pretty close to 100% of the time. It's used as an alternative to shoving pre so the scenario you described isn't a stop-n-go scenario.