When I got my XCR-M magazines for my 102, I found the bodies to be too short and wanted some more real estate to grab on to so I ordered some extensions from GS Designs.
I have these for a few Beowulf magazines and they work great, and it makes grabbing them out of pouches a lot easier, especially for shooting matches like 3-gun. I used them last year at Redneck 3 Gun and they were great.
These are really easy to install, just pop the bottom plate off the mag, capture the spring and slide the extension on. I strongly recommend the unsightly screw, as well as electrical tape to ensure the extension doesn't come flying off. The screw should be sufficient, but I always go a little over board with a bit of tape to make sure.