I've done a 1,700 mile trip 2 up with the stock America seats and a tall sissybar on my Speedmaster. I'm afraid though if I put some luxury like a touring seat on it she might get too comfortable.
Hey, I already block most of the wind for her, what more does she need?
I did get a Harley Road King pad and back rest modded for her to fit my bike, but she said that seat was too wide, so it was back to the America pillion pad. I've since taken her on a trip to Mexico and she said it was much better. Pegs make a big difference. Get some kind of platform for her feet to rest on. I've got Kuryakyn pilot pegs on the back and that really helped. Iso wings are even bigger.
