Don't be fooled by this feature that is so prominently displayed on a sticker near the door and used as a sales pitch. Per my dealer, it means virtually nothing other than you might get a few extra weeks of camping in during the Spring and Fall but that's it. The underside of the camper has that corrugated plastic sheathing to prevent water and moisture from getting to the OSB floor and rotting it out. Oh wait! Really? So I took my battery out of the little compartment on the passenger side of the camper to do some work. Beneath the plastic battery box was a 3" hole in the OSB that is there for venting. There was very little protection from probable future water damage. Just a piece of black plastic woven landscape fabric on the bottom and top. Prime Rot area! Glad I found it before any water got to the OSB and began the rotting process. I sealed the area using special tape normally used to seal butt joints of the corrugated plastic stuff and caulked where the vent tube goes down through. You might want to check the underside of your camper to make sure all areas where water could infiltrate are sealed off to the elements.
FR doesn't make any true 4-season products.
At best, 3-season.
Dan-Retired California Firefighter/EMT
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
The problem I've found with a heated underbelly is that it wastes heated air by taking it from the furnace via a hole in the duct work open to the underbelly. If you don't return the air flow which it doesn't the main cabin is in a negative and pulls cold air into it bad design in MHO as you waste your propane trying to heat your camper. I know this fiver uses more propane than my older fiver that was less insulated than this one. If it was done right the under belly would be insulated all around and sealed so you could return the air back to the furnace and keep from drawing more cold air from outside.
2001 Ford F-350 DRW 7.3
2011 25 RL Wildcat
former fiver 1976 Fourwinds had for 35 years