I don't know if they 'spread' much, but I don't think that's the problem. Even though you're using the shims, the tread on your shoes could still be the problem.
Hold it up close again and try and clip in. Check to see if there is part of the tread on your shoes stopping this from happening. Otherwise, try it on some road shoes (that don't have tread) that will accept the Crank Bros cleats. That will tell you once and for all.