80 ( +1 | -1 ) Not easy... He's going to have at least some clue about most reasonable openings. I assume you don't have something non-standard in your normal repertoire (that would really be your best bet, because you would already know the resulting postions and *might* even be more familiar with them than him)? If not maybe you could prepare something like The Vulture (1. d4 Nf6 2.c4 c5 3.d5 Ne4) + The Habichd (1. d4 Nf6 2.Nf3 c5 3.d5 c4), which are quite a surprise without being nonsense. But in general I try to play my usual openings in simuls, because I do know them quite well (and it hasn't work so badly - in the last 3 years I played 5 in simuls against GMs and scored 1.5 points, that's 1 win against Ftacnik and a draw against Wahls - admittedly Ftacnik just blundered in an equal position).