Postman and garyo, I think you're saying the same thing (?). Yeah, I thought about that, but couldn't bring myself to scar the shotgun like that just for two more shotshells.
Justin, I really don't understand what you're saying at all. Mine is an Express Super Magnum, which if anything, has a longer receiver than a std. 3" 870, and 6-shell holder wont work with it, as I pointed out, so it certainly wouldn't work on a std. 870. i.e. the problem is not "too long", the problem is "too short".