Skins_Brew
loves the smell of cosmo
That is exactly the first thing I did last year when I got my boat which is pretty much identical to yours. I did thick marine plywood from top to bottom on the outside, on the inside I didn't do the entire inside, but I added new plywood from the bottom up to the part you removed, sealed it all with sealant and through bolted top and bottom with stainless steel bolts. Basically stiffened up the rear of the boat tremendously.
I have mine on a small trailer, reregistering the boat was a piece of cake, doing the same for the trailer was a typical MVA pain in the ass. Expensive too! To retitle the trailer and register it was over $100 and I had to get it MD inspected prior to that as well! Really? a two minute inspection just to show the lights worked and the tires were good?
Really like a boat this size, far more places you can use it.
Chris Rummel
Register the trailer in Maine and save yourself the headache.