I agree.... It's as simple as Bill states it above. Drinking and driving a quad is looking for trouble.
You can do all the math..and try to figure out blood levels..etc. etc. But it still does not make it right.

Ride hard...and save the beers for the garage or campfire

 

I don't think that a persons tolerance has anything to do with BAC. I would definitely think it is only related to the amount drank in a given time and the persons size. Tolerance might be a factor in reaction times but not if they blow a .08 or .27 or whatever.
Exer

 

I play in a band far a living. NO one sees what effect 1 or 2 beers has on a person more than I do. Party after the ride. Have DEAD friends from A few beers. It's up to you,your choice,but hit my kid and are drunk, what A beating. YOU'll pray for A Cop.