Vectrix causes back pain

Same here. I think its the feet forward position combined with high bars. Try riding with your feet in a position closer to a normal motorcycle so that you r feet are taking some of your weight not just your spine / ass.

This is exactly what i found with many Harleys. As you tend to roll your spine in order to be feet-forward etc.

I guess this also depends on your height as i am only 5'7" or around 170 and i find that putting my feet as high as possible toward the front better than having them in a mid mount position on this bike but thats just a personal preference and i'd prefer to have even more length available. . Its not great and I imagine if you are any taller it could be really bad.

Just My 2c worth

I think it's the suspension! I adjusted the rear shock to the softest setting possible, but the bike still takes each bump very abruptly - I have learned to very carefully avoid bumps and potholes ;-)

Yes, I had this same issue. The lower seat option helped a lot... just a personal opinion, you should test it before buying it.

I don't have a Vectrix, instead I have an ERider scooter. I had the same middle back problem. But I've solved it by consciously relaxing my arms while riding. Keep elbows at 90 degrees and don't straighten arms like on a motorbike. Like in our motorcycle course, they say "loosey goosey". Since then I've been fine. I found myself with stiff elbows which puts all the bumps into my middle back. Whereas relaxing my elbows the bumps are now taken by my bum and soft seat.