Thanks! I got the 2500 with 159" wheelbase - it's cavernous! I've looked at some fans and dreaming up my own "idea" since I've worked on designs of fan cooled systems for enclosures. Probably won't get anywhere, so I'm looking for a system that is as rainproof as possible.Hello and Welcome! Which size Promaster did you get?
Insulation and a vent/fan will be good places to start the upfit.