I discovered this by accident or desparation.
After suffering severe back strain from more or less laying in my chair when I became tired after 5 or 6 hrs. I would slump down and it left my lower back unsupported. It finally gave out.
After about 2 weeks of getting back to a good sitting posture and visiting the Chiropractor twice a week I was doing OK but sitting for more than a few minutes was just painful. Standing up was the only comfortable position I could get into.
Tried laying on my stomach on the bed or the floor to use the computer which did not work either but was reasonably comfortable but not totally.
I had bought a HoMedics Thera P Magnetic Back Support belt to apply ice and heat and seeemed to be reasonably comfortable but I always took it off after the heat and ice was done. But by wearing the belt all the time it solved my sitting pain problem. Doesn't have to be really tight just snug it up while standing then sit down.