I think with everything in ultras, there can be varied reasons for stomach cramps and your decision to stop or push through also depends on many different things. That being said, I think before you quit you should try to take in something that will settle your stomach and see if you can’t turn things around. For me, ginger and Mountain Dew seem to work, which is funny because outside of ultras Mountain Dew makes me incredibly sick. Also, back of the pace a bit, as sometimes it is an issue of pushing to hard and drawing all of the blood away from digestion. Give those two things some time to work, and then reassess. If you still have stomach cramps, then your decision to push on has to be based on what your motivation is for that run/race and if you can still take in enough calories to get yourself through the end of the race. That being said, I listened to a Ginger Runner episode where an elite had a terrible race with stomach issues and got her calories entirely from Coke for the second half of the race. Again, the decision to do this or to drop is very personal, but just pointing out that usually if your goal is to finish you can find a way to make it across the finish line. If the point of the race was to perform well or have fun, then maybe it makes sense to drop and plan for another race down the road.