cbass929 - could it be his swallow reflex rather than his tongue? could he need slower teats? i think dr browns do a preemie teat that might suit speed wise even?
alternatively could he be just taking rests, the milk will still flow then and that will cause the dribble out? if so then a medela calma (expensive but you use just one teat) would be good as that works much like breast feeding - baby has to create a vacuum for the milk to flow, so when they rest nothing comes out at all - even if you turn the teat upside down.