I very carefully pulled apart the seat on the Miyata. The seat pan is in very good shape, just a little dirty. The foam is a strange combo of three different types of rubber, foam, and a topping that feels like soft wall insulation. The whole thing is lumpy and bumpy, and will need a total redo. The upholstered cover is actually in pretty good shape, with only one small tear. I might try to fix that and keep the cover original.