I put the 10-8 in my Les Baer, definately needed fitting but the Baer is a tight custom so I expected this. A trick I found if you have a drill press is to lightly chuck the release button up in it and get it spinning at the slowest speed, then use very fine 1000+ grit auto detailing sandpaper to slowly take off metal, trying it till the release just almost moves smoothly. Then give it a few revs of really fine 2500-5000 grit paper so lt has a real polished smooth finish (if you have a polihing wheel great, I didn't). Lastly I used a dremel sanding bit to cut the button side back just enough not to keep the mags from dropping. Took about 1.5 hours to fit being very careful.
BTW I also installed thier Gen II slide release and really like it.