I believe that the entire roof may have pinholes so I'm coating the whole thing.
It's a 1994 Four Winds 5000 which is 29 feet.  I have ripped out most of the wood and foam in the cab-over and I plan on rebuilding that when I can.  First I'm just trying to seal it and stop leaks. Later I'll reinstall the foam and put in new wood framing as needed.  It has some aluminum framing. 
I plan on cleaning the aluminum roof with TSP (tri-sodium phosphate) before I apply the elasomeric coating... unless anyone here thinks I should prep the roof differently