Thanks for all the ideas. I visited a seat/upholstery shop today. They couldn't believe the cheap build quality of the Xterra seats. No springs, lousy soft foam and you're sitting right on the frame. The guy suggested putting 1/2 to 3/4" spacers under the seat mounts at the back of the driver's seat to raise it up a bit and improve the angle. He felt that if that helped, it might then make sense to add some foam padding to the seat bottom. Alternatively, he suggested putting in another seat and had an old filthy Corvette seat on hand. However, to re-upholster and install it would run about $700! Anyway, I'm going to try the spacer and foam idea. And, I dug around and found the post on the inflatable lumbar support and am copying it below. Find the original post by searching for "Miata" (in parts and accessories)as mentioned above. Cheers and thanks again.

"Lewis Lumbar Support

www.miatamania.com (Moss Motors)
800-642-8295
parts@mossmotors.com
$54 a pop."