I think i could
Could you hold off a GM for 20 moves?

I agree with Tycho. You would have to be extremely careful, but just by being ultra conservative you could get through. Obviously, by twenty moves in againast a GM I'd have a lost position, but I'm pretty sure I could so it.
What i would like to do is play a series of odds games against a GM. How many pieces down would he have to be at the start before you could beat him? Eg:
Game 1: Me Vs. a GM:
Game 2:
I'd love to do this. I wonder how many iterations of games it would take till I got a win. Probably the GM would have to have maybe no minor pieces and one rook! We'll never know...
ED.
No, because the chess engine isn't trying to press for checkmate in 20 moves. The question isn't can you play games with GMs lasting more than 20 moves, I probably could, but would most certainly be in a losing position. The question is could you survive a game against a GM intent on checkmating in 20 moves or less?
Only one way to find out, any GMs out there want to give it a go? In an unrated game of course, and even if I make it to the 20th move I will resign.
A friend and I were discussing this the other day. Do you think you could survive 20 moves against a grandmaster? The only criteria being if the GM's 20th move isn't checkmate you win. Material or positional imbalance after the 20th move is irrelevant. The GM knows this of course and plays appropriately.
Naturally it depends on skill level but I'm assuming the challenger has a rating of 1500 or so.