That example alone is probably going to make it hard for the player vs player duel to happen. Often times, players differ in play style and position, so it's quite hard to gauge who is the clear winner, especially if both players played well. Probably easier to do this with games, as the winner is always clear.

But I guess like what GR suggested, the post creator can always set the terms and the opponent can accept or refuse or counter offer. Either way, this duel concept sounds like a lot of fun and I look forward to participate in something like this in the future. Will be even willing to put some sats where my mouth is.