Bathroom Remodel

If your coach has a steel or aluminum frame inside the wall structure, you might be able to find that frame, much like studs in a house wall, and hang your sink.

That said, I don't think even that framing has the strength you need for this mod. Even if you found a lighter sink, at least two factors work against you:

One, RV bounces down the road. This puts stresses on everything.

Two, You or somebody else may lean on that sink and find the mounting wasn't strong enough.

Thank you j-d for your post. I think you are right that's why I don't see any pictures of any like that. Maybe just a slimmer cabinet underneath. Or custom.

pedestel sink

jrobert01 wrote:
pedestel sink

X2, or find a light plastic RV sink. :p

There may be a couple other ideas but knowing the layout of your bathroom would help a lot. Include the floor plan of the bath, the hot and cold supply, waste piping and the toilet location and water supply, don't forget the cabinet dimentions.
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If yours run out from the wall it is easier, if they go down through the floor makes it a little harder.

I've got a couple of ideas but need to know more...

Is a folding sink an option?

How about making a counter top for a light fiberglass camper sink (perhaps the one you have already) then hang the counter top/sink assembly on the wall and create cantileaver 45° brackets to support it. This may buy you the leg room under it that you need.