I went out last week and after thinking about the underlay wood, decided to cut the sheets of wood in half length wise. That made a HUGH difference in the amount of work it took to get them in, especially the ones above the axles. Got all of them in except the front one and then the very front "V" section. I'm going to have to do the last front one differently because of the way the factory built the frame. The "V" frame from the tongue and the cross supports don't have the same 3/8"space between them and the "I" beams so I will have to put the plywood on the bottom of the "I" beams and caulk it up real well. The front "V" section of the trailer will not have wood under neath it as there is nothing to fasten it to so I will foam that small section in and put a heavy coat of paint on the underside of the floor 3/4" plywood.
I went to Home Depot and bought a roll of 1/8" thick three inch wide foam to put between the roof frame cross pieces and the aluminum roof. My idea was to keep the trailer as quite as possible and eliminate wear and tear on the roof banging against the steel cross pieces. It took a little less than one 50' roll to do it. In the picture, you can see the foam between the rafter frame pieces and the ceiling. I bought two rolls thinking I would need it but only needed one. I'm sure I will be able to use the other somewhere.

After getting the that done, I cut the 1" thick foil backed foam insulation for the ceiling. It went in very nicely. You can see that a couple were a little loose but that will not be a problem when I put the ceiling on.

So much for today. I need to start going out earlier in the morning and not waiting until it gets up in the high 70's.