I don't know how to say this, but are you mad!??!
The guitar chair is a very, very good product indeed and I am sure it works very well for most people with lower back issues. However (without writing an essay) I broke my pelvis when I was 21. Rather inconveniently went under a truck on a motorbike. My back issues are pretty specific around the position of my pelvis and what activates my (highly-reactive) glutes.
I went back to a traditional position with footstool with a padded bench of exactly
the right height some 4 or 5 months ago. I can't emphasise the importance of right height. The 'play' in the padding allows my pelvis to sink very slightly into a comfortable and relaxed position. Been in absolutely great shape since then and guitar chair has been languishing in the cupboard.