Look for round rather than elongated to save a couple inches.

: Are we fools to try and use a gravity toilet?

Yes, unless you enjoy using a plunger.

: I'm a bit concerned with the PA models and
: the maintenance issues there.

I've had a Gerber with Flushmate for 2-3 years now and the only maintenance issue I had was a 50 cent plastic piece breaking. I replaced it on my own in 5 minutes (I'm not a plumber) and it's worked perfectly since. I've never had to use a plunger on it - VERY EFFECTIVE! My only two complaints are the noise (it actually does startle kids), and the force required to press the flush lever (little kids can't flush it). I plan on getting a Toto G-Max for the next bathroom I remodel.