I just picked up sporter 456713 from a local gunsmith after having the barrel shortened  and d/t for a regular dovetailed sight base as the solution for the overturned barrel/crooked front sight. I saved the Criterion stub with the S&S sight base attached that is in the picture BR posted above. I'll take a few close up pics of it then I'll  try to remove it. Curious how effective the installation was after having the first attempt fail.

Criterion mills a flat to locate the front sight. It has a very slight dovetail and appears to be there only to guide placement while attaching. Holding it up  to a light there is a very small gap between the front and rear of the base and dovetail and the dovetail doesn't blend completely with the base edges either. Someone in the CMP link the OP posted said you have to be careful with l/r position when attaching the base but I don't see any measurable excess flat on either side to have to center it between. The S&S base appears to very closely match the flat width...at least on this example.   

I will get pictures up asap - going to the range to try out the new sight configuration.