I wonder if since you loved Specialized Riatas (which I have for mountain) if your Sidis aren't too narrow. I honestly find the Riatas a bit wide for my narrow feet and Sidis fit like a glove.
See if your LBS does a cleat and shoe alignment fitting. Since mine sells those Alines, we determined with my Sidis and stock insoles my high arches weren't getting aligned. They did this with the Aline system that uses lasers. The insoles Sidi puts in was causing all my pain. I was literally in tears by the end of a ride, not the way it should be. Now I have my pretty blue Sidis which are nice and narrow but I also have happy feet!
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan