I did the same thing, with sandwiched Styrofoam and sheet of heavy plastic for the ice side (used for around bathtubs) with 1/4" ply facing the shantt. Worked wonderful and made it warm and cozy in the 4x4 hub. This year I got a 8x8 otter, so I just got those puzzle floor foam pieces, as I don't want to drag two sheets of heavy ply with and I suppose the floor mats might achieve the same effect. The nice thing with the ply was that the buddy heater dried up the floor and it did feel like a more permanent shanty that way with no cold from the feet, I even thought about bringing a change of shoes as I was getting too hot in my boots. If the mats alone don't do a good job, I might have to rethink it and I guess I would do two 4x8 sheets that fold into 4x4, and drag those out. My previous ones also fit on a smitty sled and all small items fit right into the holes in a bucket so the entire thing was able to be dragged effortlessly. I would avoid making the skis a permanent piece of the entire setup, as I think you'd get better results from the wood sitting right on the ice. With a Smitty Sled the whole thing can be about foot off the ground so you can clear snow.