John J. wrote:
r1bqkb1r/ppp5/3p1nn1/2PPp2p/4Pp2/1NN2Pp1/PP2BBPP/2RQK2R w Kkq - 0 16

In this position Cottrel played Bg1. What's wrong with hxg3? I don't see any
immediate attacks by Black.

The basic difference is that f4 becomes available to the black knights
after hxg3 fxg3 or Lh6. I can't say if that's enough for the pawn. Do
you have a game score? Looking for masters games in this variation may
help in the evaluation.

Cottrel also doesn't appear on FIDE's Elo list. It may be that he (or
she?) doesn't have an Elo which might also be an explanation.

Claus-Juergen