1)...stability, as wide as you are and keeping all heavy items down low(ie.water, propane, batteries, etc) you shouldn't have a problem...just don't go driving the Dragon at 90 and take it esay until you have a feel for it...your biggest problem will probably be wind resistance...even wiith the curves you are pretty tall
2)...try using a polyurethane grade contruction adhesive such as PL or SikaFlex (or others)...of late, an adhesive by the name of Henry's 663 Outdoor Carpet Adhesive(or similar product) has come into favor among many here on the board for attaching Al skins...it is trowel grade, waterproof, stays flexible, has a long enough working time and is fairly easy to work with
3)...ABS tanks have fitting available that can be directly glued in place...if you cannot run the shower drain directly into the top of the tank, set up the drain to the tank like a "p" trap...with the drain going directly into a 90deg bend, and another turned straight up and another going into the very top(side) of the tank...
4)...any other questions???????
madjack

...I have come to believe that, conflict resolution, through violence, is never acceptable.....................mj