I'm testing the seat from Aeroclassic to see if the lower cost back is thin enough. If not I will have local boat seat company cover my phone. Notice it has about a 9" piece of foam for lumbar.
Jeremy at Aeroclassic has sent me a trial of their lower cost back. I'm trying it now. It still feels thick, but with the bad weather I have not flown much and need to try it a bit more.