Hi @retirement75 and everyone in the group I have been following this thread since it started and wanted to chime in as someone who has dealt with similar butt and lower back pain from long hours at a desk and in the car. Like @johnbishop mentioned I started with a basic U-shaped cushion for my tailbone and it helped short term but after reading the Verywell Health review @johnbishop share , I upgraded to the ComfiLife Gel Enhanced Seat Cushion. It is a game changer for me the gel infused memory foam molds to your body without feeling too firm, and the U-cutout really takes pressure off the tailbone and sciatica spots while supporting the hips and lower back. I have used it on my office chair car seat and even a recumbent bike like @johnbishop and it stays put with the grippy bottom. No more shifting around!Echoing @pacer3702 on the Cushion Lab which is awesome for spine pressure relief and super comfy for driving but I found ComfiLife a bit more responsive and affordable for everyday use. @coachdavid McKenzie tip is spot-on for lumbar-specific support pre surgery too great for targeted back alignment. And @bnancy the ComfiLife is basically the upgraded version of what you have same brand family but with added gel for cooling and extra bounce.
If you are still experimenting on Amazon like the OP I would highly recommend trying the ComfiLife one I linked below. It is doctor-recommended for back/sciatica relief has over 50,000 reviews averaging 4.5 stars, and it is versatile for chairs cars or bikes. Fingers crossed it works as well for you as it has for me hope everyone finds their perfect fit soon