There's a plumbing diagram for your coach available here
Looking at it, I'd say your toilet is directly over the tank. It seems to be a shallow tank, though, which I suspect makes the pile-up problem more likely.
I had a coach that did have a shelf immediately under the toilet. I learned to put plenty of water in the toilet before use. That was done by lifting the flush pedal (keeps the ball valve closed but admits water).
You may also want to start with some water in the black water tank. I know it shortens the boondocking duration-before-dumping, but your aim is to keep the solids from sticking to the tank bottom immediately below the toilet discharge.
P.S.- If you haven't already done so, you may want to download all the relevant files for your coach, available through this