Never mind -- I finally figured it out! Just in case someone is as dopey as I am, I'll answer it.
The mandrels are indented on the right hand side! This is NEVER mentioned in the manuals. You need to line the holes up with the thumbscrews before screwing them in. Duh! I was blindly screwing them in, not realizing there were indentations there. Makes all the difference!
Laurie
December 2012