I would never try to level someone's game on location. 1st you don't have access to the PF to do it properly. 2nd IT'S NOT MY GAME! I'd finish my game and be done if it was that bad.
Side note..... I'm always amazed how many games at Pinfest in Allentown are slope challenged or way off level side to side. I've played one ball on so many machines and just walked away. Why try to sell a game in the free play area with a miserable 3 degree (or less) slope where the ball just lazily rolls down the PF? Or games that are so off side to side you laugh when they give you a gravity drain from poor leveling.