Conventional wisdom always seemed to be two pints of 4% beer (i.e. around 4 units of alcohol) was under the drink drive limit for an average male. However there are a bunch of variables including age, hydration, food, how much you've been drinking previously. You've said you want to discount absorption time (again conventional wisdom was that it takes an hour for the alcohol to get fully into your blood and then you process it out at the rate of one unit every two hours) so I suppose the simple answer to your question would be you can knock back 4 1 unit shots and then drive and theoretically be under the limit. Although doing so sounds very unwise!
How wrong is my common knowledge on this?