There's quite a few years between our '66 coach and your '02. However, I was faced with the same delima 3 years ago. Our rear bath had rot from streetside to the curbside. At the time pulling everything forward out was not an option. So I pulled the belly pan, black tank, toilet and the exterior body trim (which exposed much of the floor edge). I was able to replace much of the rotted floor, in sections from underneath. It took making carboard templates and transfering them to new plywood. After dry fitting from underneath and sliding the ply in from the uncovered edges I coated both sides and all edges in fiberglass resin to water proof it. The floor is quite firm now albeit for one squeek...which IS kinda nice
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Neil.