s114 - Thanks for the best reply yet; sitting higher than normal is indeed good info. We are tall as well so sitting a higher probably won't pose a problem. Our type of camper use really would find a cassette preferable over a bk tank.
Good to know on the pressure thing too jmckelvy. Reminds me of a trip many years ago in our Blazer with a porti-potti onboard because our daughter was toilet training. Went through an elevation change in Yellowstone. She peed. Momma open the valve and we had our own little eruption right there in the car! Course I'm standing outside waiting, wondering what's taking everybody so long. :)