Recovering from herniated disk and nasty sciatica, I suspect that riding my relatively slack Lemond Zurich frame with shorty aero bars contributed - as did many other things. In theory I can ride a well fit triathlon bike and improve my comfort and open up my hip angle a lot, which should help. I wonder about others with back problems and if you picked a particular frame style or solution?
If you have had back problems, how agressive did you get with seat tube angle? Did your back improve enough over time to change your setup?
What have your physical therapists recommended? Mine took a look at my position and made some suggestions. After my back got better I was able to do what I wanted with some minor adjustments (not as low and extended).
I had a herniated disk and still deal with lingering sciatica. I am most comfortable with a seat angle of around 82 degrees. The steep seat angle also allows me to get low in front, transferring weight onto my arms and off of my back.
I rode a Softride for years thinking it was what was helping my back when in fact it was just a steep seat angle that I needed.