Hoellander aluminum speed rail and aluminum pipe is a great alternative. I used 1-1/4", but would strongly suggest going smaller, this thing is way overbuilt. The sheet metal and supports will give out well before the rack. 1' or 3/4" sch 40 pipe would have worked fine.
I have also built an awning that attaches to the pipe out of 3/4" PVC but don't have any set up pictures.
The entire set up cost roughly $200 after some shopping for fittings and pipe. The rack held up to an 800 mile road trip this last week, now on to interior work.
A few tips picked up from others on this forum or elsewhere.
1.Don't forget, aluminum in contact with galvanized = rust. Hoellander states on their website says the fittings and flanges are coated and won't cause rust, but a piece of rubber is cheap and easily placed between to keep them separate just in case.
2. Polyurethane sealant works great, but takes a week to fully cure. It will last longer than most other sealants with UV exposure.
