Ok, so I'm looking to buy a 19" coda sport online but I'm a little stumped on sizing. I recently went to a trek store and the guy had me get on a 7.5fx bike and after raising the seat 3 or 4 times he said a 20" would work. After thinking it over a few weeks, I decided I might like a coda sport or coda comp better. I have read that a 20" trek is comparable to a 19" coda so I thought I was set on sizing. However, I found a few websites suggesting putting the spine of a book against your crotch and measuring to the ground. After doing this, I got about 33.25" which would suggest a much larger frame. I'm about 5'10 and in most threads I've read, people 5'8 to 5'11 are usually riding 19" jamis bikes. I will mention that I had scoliosis surgery at 16 so that may somewhat explain the long leg length at my height (the curvature probably takes 1.5-2" off the length of my upper body). So do you think a 19" would work or should I get a bigger frame?

Edit - not sure if it matters but the 33.25" is without shoes. I wear running sneakers so about 34.25 with shoes.