at which a D-1 guy and 4 gals on BYU can beat 5 gals on UConn.

I concede that break-even point would have to be a lot higher than D-1's worst player. It'd need to be someone good enough to be worth more points than 2 of UConn's 5 (as in, scores alone more than he alone defensively allows two of theirs to score), leaving essentially a net-4-on-3 in BYU's favor for the rest of them. And even then, whether 4 of BYU's best could beat 3 of UConn's best could still be debated.

That 1 guy would have to be pretty good not to be able to be worked around, both offensively and defensively.