I always leave my cover on too. I take it you also have the aluminum bracket on the top of your seat back(?) Anyway, at first I was going to use some 2 inch thick foam stuff I got from my nephew (they use it where he works to deaden compressor noise, but it holds water like a sponge) and fill in the seat back. Then my buddy says REM makes all that stuff (true) , so I looked and they link you to places like Legendary (which showed nothing for convert) or Dantes (who I called). Maybe Ma just didn't think it was a requirement???