Here are a few things to remember, Sunforger is a treatment...not a canvas...you can have Sunforger treatments put on any fabric, so the canvas is as important as the treatment. A good 10 oz
pre-shrunk cotton canvas with a tight weave is about all you need for a good camp. If the treatment is put on the fabric after it has been sized, most of your treatment will end up on the ground after a good rain, it should be put into the fabric, then sized to get full benefit of the treatments.
A mildew resistant fabric treatment is also a good idea, I was at a rendezvous and watched an eighteen foot tipi turn gray in five days because it had no mildew treatment and the humidity was about ninety percent.Dampness is a breeding gound for mildew.
I saw what was left of a tent in PA. a couple years back that had no flame retartant, went up like toilet paper and didn't even scorch the tent next to it that was treated with flame retartant.
The option is yours, but for the couple of extra bucks worth of insurance, Get the best to start with. You are not saving money by buying cheap, you have just waisted the price of the tent.
( in my humble opinion )