Are you sure it's the caffeine? I ask because I have no problems at all with caffeine, but coffee in any real quantity, eg. more than in a Coffee Crisp or coffee cake, gives me stomach cramps, but I can take a 200 mg tablet on an empty stomach and have no problems at all.
Everyone's different, and I'm curious if this is another of those.
I limit myself to the caffeine equivalent because I don't want to build a tolerance. As long as I stick to medically safe levels of caffeine I don't seem to have any side effects, just more alertness/energy, so having to take more to keep withdrawal symptoms at bay as well as having to take even more to see any benefits just seems like a bad idea.