Your estimates don't work. Over 10 years ago I was that DD. A bunch of us got together to play cards. Leading up to this event, here were the details: Got off work and went for a two mile run about 5:30 PM. When I arrived home I got a call from a buddy that we were playing poker that night so I showered up, grabbed a six pack and headed out the door. Got together around seven and played cards all evening. About 1 AM the game was breaking up, one of my buddies was smashed and in no shape to drive. I had drank 6 beers over the course of about 6 hours, 7pm-1am, I'm good to drive, I'll give you a ride home. Dropped him off at his house and headed home. Got pulled over for doing 30 in a 25 (cop was obviously just trolling and pulling anybody over at that hour of the night). Ended up I blew a .12. Could not believe it. Must have been the combo of exercising and not eating. I thought I had done what I should have been doing, drank moderately and didn't exceed one beer an hour, didn't feel any buzz or anything, still got popped. Ended up costing me money and now I can't even get into Canada cleanly.
F drunk driving laws. They are absolutely stupid. They make no sense and are just a cash grab. They've gone way over the line when people who think they are being moderate, that think they are trying to do the right thing, still get caught up in a web of laws and are busted. I don't mess with it anymore, one beer and I won't get behind the wheel because it doesn't take anything at all to get pulled over for a DUI these days. Remember that the next time you order a margarita from Applebee's and drive out of the parking lot, you are probably "over the limit" and could be setting yourself up for a DUI.