Starcraft Travel Star Restoration

You shouldn't need any dimensional lumber as big as 2x6. You should have some type of framing that supports the composite panel floor. I'd suggest to remove all that is damaged, including bits underneath walls. You can use an angle grinder or sawzall to ferret out rotten flooring underneath the walls. Support them with small blocking until you install a new floor. I'd suggest to install a conventional framed floor using 2x2's with foam in between floor joists. Sheet the floor with "X" rated plywood, a minimum 5/8" to offer support on a 16" OC floor. Slide your new floor sheeting underneath the walls while removing the support blocks.