new trailer

Hello 2 friends and i bought a new to us used sled trailer. It is insulated and heated, but the under carriage is not insulated, and the floor inside is just plywood. Would like to insulated under floor and do something with floor inside. Thanks for all suggestion ahead of time
p.s. Also it has an under belly propane tank, how do people fill those, besides going to a gas stn.

My old trailer and current trailer is insulated with plywood floors. Unless you are planning to sleep in the trailer i would not spend the money to insulate the floor, we have never had an issue getting the sleds melted with a plywood floor.

Spray foaming the underside would be the ideal way to do it if you are set on it. I had this done to my RV, be sure to run a hitch sweeper/rock tamer set up. The foam gets blasted pretty easily. I can imagine that the road salt and sand would not be nice to spray foam.