The repop seat padding kits being sold for reupholstering the seat bottoms and backs indicate they include a layer of burlap (maybe 1/32"), a layer of cotton batting (approximately 1/2" uncompressed), and a 1-1/2" thick foam pad that goes on the bottom section before topping with the seat cover. Most appear to include just one (1) sheet of the foam for the seat bottom, so the cotton batting and burlap sheet is used for the bottom and then on the face of the seat back before covering.
I think a 2" thick foam pad would probably simulate an appropriate seat bottom thickness for test purposes. Perhaps a double or triple folded thick blanket (don't use the other half's good blankets -
) laid on the back seat section would be sufficient to simulate that thickness.
