Last year on my Raleigh R700 I pulled a YAK BOB trailer and I had installed a rear rack which I had some light panniers. My Raleigh had rear eyelets at the quick release location, but nothing up on top near the seat. I found a seat clamp which also provided upper eyelets for a rear rack.
Your Scott probably doesn't have either the top or bottom eyelets. This seat post clamp will fill the bill for the upper rack mount point...the bottom eyelets you'll have to figure out, maybe some rubber insulated clamps of some sort?
A standard rear rack can handle far more weight than a post mounted rack. This might be an option for you.
Oh yeah, my R700 didn't make it. The steering head tube developed a crack, which made it impossible to keep my fork tight. After 1000 miles I was done and had to abandon my trip. I have since bitten the bullet and purchased a Surly LHT. She's taking me across again in 2012.