Noz, If you're referring to Dremeling the edges of the cylinder that wrap part way around the Nipple recess, I've seen that information. I haven't done it yet though - I'm waiting till I get more experience with a Dremel tool so I don't screw anything up.
claypipe, I've seen long skinny cappers at Cabela's and at online outfits that are touted as being able to fit into Remingtons (mine came from Cabela's). I didn't get mine directly from Ted Cash's web site but both of my cappers are stamped with his name on them. They may be what you're referring to. They both fit my Remmie fine. My brother got one for his Remmie at Cabela's and his fit fine too.
I did buy one online on one occasion that didn't work. It looked from the ad that it would, but the prongs on the end (that hold the cap in place) were different and didn't fit. I gave that to someone who didn't have a Remmie (a feeble attempt at "passing on" some of the generosity that's been shown to me by all my pards).