It's done now. 2 layers of burlap, opposite directions for strength, 1" thick jute I had laying around and after initial fitting, added 2 layers of crappy cotton batting I bought for another project.
Backrest is done as well, THAT was a biotch to get enough padding in the top and then pull down to ring the bottom and sides. If not for my lovely and ever helpful wife, it would not have been done. Speaking of her, she came to the rescue 2 other times. When disassembling I came across an interesting piece of burlap that supports the top of the upholstery and keeps it tight at the top. It was in bad shape and she made a new one in about an hour from new burlap and listing wire on her sewing machine with a zipper foot. Fit perfect. Then, as we were pulling the bottom listing down to attach, one end of the sleeve tore out about the last 4 inches from the end.. not a good place to skip rings at. The sewer at Legendary let the overlap edge get too close to the thread and it pulled out. Again, my wife brought her needle and thread out to the shop and sewed it up and we moved on like nothing ever happened...