With thanks to the "75/31' valve repair" thread, here goes a slightly different effort on a mid-bath. By the way, the photo in the other thread looks like a mid-bath, too, from what I see in the repair manual, here:
http://www.airforums.com/forums/394393-post5.html
I don't see any access panel and the belly pan is tucked inside the frame in a way that will make it almost impossible to remove, so my first step will be to cut an appropriate access hole, to be covered later with a new panel.
I'm lucky to have gotten the 1975 Maintenance Manual with the Sovereign. This manual covers every model and variation, which gives some hints as to where wiring, pipes, and tanks are in other 70's trailers. Woohoo, as my daughter would say.
The frame is clearly "stepped" in the photo above, but I don't see that in the drawing below. I guess I'm about to find out if the grey and black tanks are on different levels and why.
The tank drawing below matches well with the photo in the link above.
The scary/aggravating "news" from step "f" below is that the valves are glued in and must be cut out to repair. I can't wait to see if there is a better scheme for reinstalling them. Right now I only need to fix the gray valve.
Plan of attack:
1. Cut large access hole.
2. Take a long look.
3. Come back to forums and see if anyone has some good ideas.
Zep