Another seat cushion option:
http://www.shapefitting.com/ProductI...tid=AHPLANESTD
I do not use the aviation specific model, I chose instead the 4" thick version designed for people in wheel chairs.
I have spent the majority of my approx. 10,000 hours flight time doing long- line (vertical reference for those that are not familiar) work and I must say that this cushion saves my back like nothing else I have tried. I only wish I would have found it 15 years ago.
I only inflate it about half way (say about 2.5 inches) but the 4" model is tall enough so that as I lean out the bubble the cushion squishes down on one side and raises on the other, in effect tilting the seat for me while still providing full support across both sides of my butt. What actually happens is air transfers from cell to cell inside the seat, deflating one side and transferring the air to the other side. When I leave the bubble window and move back inside to an upright position the seat levels out in about 5 seconds giving me a comfy level seat.
For a pilot that does not do vertical reference work the 2" thick cushion would be perfect. For the wheel chair specific models you can get them in any size you want...just measure the seat in your machine to see what size you need. There are TONS of sellers of this product on Ebay. Just type in "Roho" in a search.
Think about it.....this technology was designed specifically for people that are sitting in wheel chairs all day every day..and it works!