It is an 8.5x20'. Chavey2 how long is your trailer? I was trying to not have full runs of Etrack but it will be recessed and welded to the frame if I have the manufacturer do it.
Mine is an 8.5x24, but I'm also turning mine into a full camping toy hauler too. (Kitchen and bathroom in front, beds along the wheel wells that fold up.) I only put the 5' pieces of e-track in and the rear of the SS is still a couple feet in front of the rear door. Basically, if you keep the wheels of the SS on both sides of the wheels of the trailer, you're going to be good.