Spray foam insulation works well, clean the area to cover good then having a disposable trowel handy,( cement trowel works good) as the spray rises, expanding use the trowel to maintain thickness. Practice on a piece of cardboard before you try your boat. in order to smooth it better use a belt...
Have you thought of using split doors. Build or buy a door that fits an split it down the middle, hinge both sides and half swings to each side, use good wood no warpage, and they look and work good for small entryways...
I also have a 25 foot Apollo, it's a good stable boat in rough water and handles well at high and low speeds... One problem I did have was water hydraulic locking the engine once when the thermostat didn't open, the engine was getting hot so I shut it down when it finally opened it sucked water...
