Update....and I decided to go for it after some more thought and realizing that I didn't have to cut into the floor for a little looksee. Removed the starboard side tag wheel and then the grey tank cover, which I hadn't realized before. Got lucky after removing a block of anchoring wood in my way and saw a light crack in the top of the 1 1/2" drain next to the tank. Shimmed up the tank rear a little since there was little clearance under it, for what I had in mind. Now, here's a situation with a small working space almost at arms length and one where you can look with a flashlight and then put your left arm back in there to work, but not both. Bad enough with one hand, but having to feel your way, makes it more difficult. Anyway, after sanding with emory, as best I could and using a rubber glove, I smeared this marine plumbers goop type substance all over it. Tested it after a days drying and no leaks, but not stopping there, so bought a 1 1/2 - 2" rubber coupler that comes with two SS clamps to put over it. Thing is, you can't slide it over, like design, so cut it and fed it around the pipe with the split on top. Filled it in between with the goop and after a little drying installed the clamps. Now keep in mind that this is all being done with one hand and mostly by feel only. You might try putting one of these clamps together with one hand and getting the tightening screw started sometime, although not a bad as first thought and actually had little trouble with those. After tightening with a nut driver, I applied another coating of goop along the top, so I feel it's good to go in that area without any future problems.
All this time, I was studying possible removal and reinstall of this tank and now feel that it could be done with some difficulty and without cutting a hole in the floor. A lot of it would depend on being able to get to the other side under the wheel well and where the bath room empties into the tank. There's small access there with a plate, so enlarging it, would probably be necessary at best.
I managed a few pics on iRV2 forums
Grey Tank Leaking, but can't figure how to upload them here, so if someone could help with that, please.