Thanks very much to both of you--On your advice, I will try a seat with a cutout. I doubt that the 60/40 split or that stem length is the problem because I have actually been on a small bike, a little too small for me even (sin! I am getting a new bike ASAP).

Went out today for 100k, mostly flats and rolling ascents, and the urination after I got home wasn't as frequent as it was last time, or perhaps just, as I had imagined! Anyway, thanks, and I'll update the site on the results.