Chainstay Overview Drawing & Choosing Chainstays
Draw in the rear axle OLD (130mm), the thickness and length of your dropouts including tabs and slots on the chainstays, the overall chainstay length, the width and (inner) diameter of your BB shell, and the distances from the BB shell face to the outside of the chainstay sockets. Also draw in your tire diameter at the appropriate point. Choose some chainstays that will line up with your drawn-in dropouts, clear your desired tire, and meet up with the drawn-in BB ports. I ended up going with these mildly S-bent Columus Zona CX chainstays to clear a 650Bx42mm tire -- the straight chainstays I first tried would've needed a lot of crimping to work.
Also scribe a line on the inside of the chainstay as held over the drawing, at the dropout -- this will let you determine the proper slot angle to cut for the dropout tab. Mine was 12°.