Sorry, I can't give advice since I only hit 20MPH on the downhill.
There's very little information on cycling and scoliosis out there, but everything I've read suggests getting as 'stretched' as possible is the best way around the problem. I'm very upright by most standards, but the lower I get, the better I feel. However, I've never been able to feel entirely comfortable on a bike, and I suspect you might have to accept a certain amount of discomfort as well.