Diameter is a problem, but a sidekick stock is your bigger problem. The sidekick frame is about an inch shorter than a SB1 or 2 frame, therefore the forend is one inch longer from the hinge to the forend screw. The inside of the sidekick synthetic stock is hollow and built up only around the screw base, so you can't really drill another hole to fit a normal barrel.
I will get some pictures on here after work to show the differences in sidekicks and rifles, maybe Tim can post them in the FAQ.