If it's anything like the UKicon competition forsight block bands, they were just normal ones with the foresight bed machined rioght down and a new longer dovetail cut in to allow for the P-H tunnel foresight to be fitted. So said, the modified foresight block wasn't either wide enough or man enough to cope and the tunnel foresights were constantly working loose in the blocks.

Mathematically, there's no way that a tunnel foresight can be made to work on a standard un-chopped foresight block band. Well, it COULD, but the foresight would be far too high to do any shooting with. You could raise the backsight but............