Hmm.. i'm not sure if this answers your question, but I think the double cranks need 109.5 and triples need 118?? I'm doing the same pairing on my cannondale. I have a 109.5 DA and a double 105 octalink. What are the rest of yoru drivetrain components? Is the rear a short cage? If you aren't making this thing into a fixed gear, I think a 2 mm difference in chainline is not going to make a whole lot of difference. you will end up fine tuning the derailleurs??