Made these up the other day for the Jayco using 100mm pipe.
You can get pipe and brackets at 150mm but I couldn't fit those where I wanted so had to go 100mm, it's all about your space.
The pipes and brackets can be purchased complete CaravanLand in Perth sell them with brackets for about $110?? I think I made my two and bought brackets for less than $100 and built then to the exact length I wanted. The jayco curves and I don't want over hang.
I can get six large poles in each with careful packing, (jayco poles have huge locks hanging on the sides!)
Matt