I've been building a topper for this unit. It is within an inch of the ladder rack setup height. Fully enclosed to stow my basic gear out of the garage and shed. The aluminum material is a combo of 1/8 angle and channel, 1 x .090 square tubing and .050 panels. I used the sides doors off an ARE cap which I cut down in height for this project. The roof is a narrowed/shortened Land Rover Series roof. My RTT will go on top using an older Thule rack setup. Despite it's height it is very stable. It tows at speed and in curves very well. That is probably because the trailer is quite heavy bringing the CG down.
