Re: And so it begins...
My trailer set-up sounds to be exactly like yours and I hate it!! It is very difficult to get it centered when reloading. I'm going to eventually get much larger keel rollers and maybe new roller bunks. My trailer is rusty and needs a bit of work but I'm hoping to get another year out of it as is since next year's project is the transom. I used 3/4" pressure treated ply on the floor. I didn't seal it with anything because I didn't know any better (I hadn't found this site yet). I didn't have foam in my boat really. Just some pieces of construction styrofoam that the previous owner put in. I left most of those in there. I think if I were to do it again I might consider the pop-bottle method. My boat is a bit leaky and I'm afraid to put in pourable foam and have it end up getting water-logged.
As far as the transom goes.....on these boats the transom has nothing at all to do with the floor so one project really doesn't have much to do with the other. So if yours isn't rotten there's no compelling reason to do it now. Mine is completely rotten and was when I got the boat. However, the previous owner had reinforced the whole thing with a large peice of angle steel that the motor is bolted through. It is very solid. However, everything that is bolted through the rotted wood leaks like a sieve. So that's why I'm finally replacing it. I'm not looking forward to it. I'm really hoping to be able to do it without dismantling the splash well.