Out of curiosity, I searched the FAA incident database for "kidney". In 28 years of records, it came up with only 8 incidents of kidney stones, and all of them were air carrier incidents. All, of course, ended fine with the other pilot landing. I think this shows evidence that sudden, truly incapcitating pain from kidney stones is very rare, and is a non-factor in general aviation incidents/accidents. Much like how the FAA medical folks hamstring people who have undergone chemo (I know someone in this situation) - they are setting standards that have little to do with legitimate, statistical probabilities of in-flight medical problems endangering the outcome of a flight.
Has anyone ever heard of a GA pilot having a major kidney stone incident in-flight?
I'm certainly not advocating that it's a good idea to go flying with known unstable stones, but I'm looking ahead at what I'm going to need to go through to get flying again and how much it's going to cost me on an on-going basis, and I'm not at all happy about it.
Jeff