I tend to echo Toad's sentiments on this one. Having suffered with back pain in the past (herniated disc at S5L1, now repaired), I know the agony and the need to feel like you have massive support in the lumbar area, but it's not always the ideal solution.
With the adaptive sports seats in the 911, I have 14 ways of moving the seat including lumbar support from the base right up to the shoulders, and I used to whack the support full max at the base as that's always what I was told was the right thing. It never really helped, so once I got fed up with the pain I started playing around with the seats to see what else could work. In the end, I settled on a far more upright position than I would normally use, and whilst it felt incredibly odd at first, and made me look like one of those dozy old women in their 90s you see driving bolt upright, it helped massively as I'd improved my posture rather than just supported the problem area.
The Zed seats aren't the greatest in terms of support anyway, so my recommendations would be to try and give yourself a better posture by moving the chair, and definitely purchase yourself a CG Lock if you don't have one already. Both of these together should give you the pain relief you require when driving.