I use an enclosed trailer to haul my kitfox and haven't had any trouble with rubbing the sides. My trailer is 8'6" wide, legal in all states, and works great as a hanger when parked in a tiedown spot (I did exactly that for a winter in Florida. They charged me $30/month for the spot)

I put straps over the wheels to hold the mains and support the tail with a stantion that I made. That keeps the plane from moving around, but I was also concerned about the fuselage swaying as the trailer bounced. I attached eyebolts to the trailer floor under the planes forward float fittings and use ratchet straps to go from the float fittings to the eyebolts. That stops "body sway" and makes it impossible for the wings to bump the sides of the trailer.

I have about 3000 miles on it with NO RUBS.