Capt Al ,
I have that cushion , and I too am having back problems. I have swelling / inflamation just above my butt. Its really a pain in the ass. Pun intended.
When I went to have the chair fitted , there was a different cushion , and it was too small. It was still more comfortable. It had different bladders sewn around the cushion.
I will bring this up at the Rehab clinic on Monday.