medic09, Sprints aren't really designed for upright riding even for taller folks. I'm in the middle at '5"10 and I don't sit
fully upright. Your feet are always going to be slightly behind your hips. The risers are just supposed to give you a little more relaxed but still forward position. I don't know if there are any taller risers out there or if they might compromise your ability to control the bike but you might try the old google or go to the gears and gadgets forum and ask there too.
I would have suggested the Tiger for a more upright position but at '5"7 it would simply be way too tall a bike for you.
Hmmmm? Wish I had more to offer.