Ultimate Gel Seat Cushion
This seat cushion takes the hard XF (MB) seats & makes them really comfortable. The ad shown is from ebay but it is available during December at Costco for $14.99. I have been using one over a year & am really happy with it. I am 5'10" & with the seat lowered all the way to the bottom I still have head room with the cushion. The only disadvantage is that the seat heater isn't available. I also have one of these on my desk chair.
http://www.ebay.com/itm/like/272009285905?ul_noapp=true&chn=ps&lpid=82