I recently move my spare tire from the rear bumper to under the front of the trailer because it was in the way of the bike rack and travel tray. I used unistrut which I purchased at home depot in the electrical section. I had to keep the unistrut close together as possible so there would be room to get the tire on the rack. I think most trailers have the room under the front to accomplish this.
Looks good but also looks like a PITA to get the tire out. Especially on the side of the road, in the rain. Which, as you know, is when most flats happen.
2013 Toyota Tundra DoubleCab 4x4 iForce 5.7 2014 Grey Wolf by Forest River 26BH TT