[Wally Arntzen]

Charlie, on my 88 I have a foam block that is about 5" thick, 8" high and goes accross between the water tank and the waste tank. If you have something similar try pulling it out and see if you can move the waste tank toward the water tank a few inches. If you can is it possible to push in a steel plate 1/8" or more between the waste tank and the wall of the next bay.If you can you could cut holes in the bay wall and repair the leaking plugs, pop rivit patches on the wall and you would not have to remove the tank.
The need for the plate would be to protect the tank so you don't cut or punch holes in it while cutting the hole in the wall.
I would try all options rather than take on removing the tank which could open up all kinds of other problems.
If you measure from the edge of the tank to the plugs you should be able to duplicate it on the wall and cut the holes where you want them. With the steel plate you can use a sabre saw with a short blade or some good tin snips if you have.
All coaches are so different so what I am suggesting may or may not work in your situation.