lower back pain? would that be your pelvis trying to rotate forward but something is stopping it, so it shows up on the lower spine?
happens when the saddle position is restrictive(or having that as side effect from something else), and you cant extend your legs. +1 on high saddle.
The STARTING POINT for measuring saddle height is your inseam in cm x 109%. top of the pedal spindal to top of saddle. It doesnt need to be correct at first, just for REFERENCE. Just need to ballpark to see if you still get lower back pain with that "rough" "reference" saddle height.
https://www.cyclingabout.com/saddle-...touring-seats/