Here are the specifics: Current bike is a Litespeed Sirius, 9 speed double, with a Shimano 105 (FC-5502) Octalink crank that has been professionally shortened to 148mm. New bike coming in soon is a 09 Look 566, 10sp double, with Ultegra SL crank and components. Assuming that the Look bottom bracket will accept the Octalink components, I want to replace the 10sp Ultegra crank with the shortened 105 crank. Shortening the Ultegra 10sp crank or any other 10sp crank is currently not viable and is not an option. The shop that shortened the crank said that I can purchase 9/10 sp compatible chainrings from FSA and they will make my FC-5502 10sp compatible. My LBS said that if I try that terrible things will happen like my frame will crack and the rear derailleur will buckle. Referencing Sheldon Brown's website, many cyclists have just changed to a 10sp chain and have not had any problems. Now it is my understanding that the inner ring is closer to the outer ring on a 10sp crank vs a 9sp crank. If that is really the case, why can't I just take my FC-5502 and mill the inner ring mounts to match the spacing on the 10sp Ultegra? I'd appreciate opinions on the FSA chainring option, is my LBS correct and is milling the proper path forward? Any other ideas?