Wow, a jet ski and no back pain??? What??? Lucky man! I think my skidoo-ing years along with heredity is behind my back problems....Good thread so far. I also suffer with LBP and stopped riding a couple years ago because of the pain. I had cruiser seating type bikes and more than 30-60 min could flare up bad pain. Did 2-up touring with the wife but had to switch to a convertible. My back has improved but i'm yearning to ride again, badly. I'm average height but short legs. I'm leaning towards lighter bikes with better stance for LBP. Something that could occasionally accommodate the wife 2-up too for short trips. Picking a bike is HARD. I'll be following this thread.
P.S. I ride a jetski too and never have back pain. Can't really make sense of it.