Don't know if you have a problem using Norcold or not . . . but their model "N410" is almost exactly the same size . . . I take that back, it is exactly the same size as the RM 2452.
My installation manual says that the cabinet/box should not allow any air around the sides or top - only provide air space at the back. So I'm guessing that's how yours was installed (with very little wiggle room).
Good Luck, PM me if you can't find a source for the Norcold.
Aluminumbskull with Led Balloon in Drag
Birch Plywood and Aluminum go together like
Peanut Butter and Chocolate