I don’t do sportsbooks, so maybe I am confused here, but hear me out…
You say that the sportsbook can’t be in the hole overall because they balance the action on both sides of the line. However, don’t they pay you a commission on what your players lose, not just their vig on the bets?
Let’s say I have one player and you have another player under our respective 20% commission accounts. Each bets $1000+$100 on opposite sides of a game.
If my player wins, I’m at negative $220, but you get paid $220 in commissions.
If they cancel my negative, then yes, the sportsbook is in the hole. Right? They made $100 on this bet, yet they paid out $220 in commissions.