Not that this info may be useful, but I have a sealed tank setup for my IC system. Even when running the crap out of it in southern Georgia have I never had pressure built up when I removed the cap. Also the water would get hot, but where I could stick my fingers in it and it's not uncomfortably warm... how's THAT for a technical analysis? lol

It will probably be another month before my car is back together, but I guess that water temp sensor I put into the IC coolant reservoir might prove useful.

FYI, my setup:
Stock HE, Ford Lightning IC pump, stock CAC, and 1-gal aluminum tank w/sealing cap. I also have a 2-pos switch that allows me to switch the pump on, with the car off, for cycling ice water at the track.