I just did a mod to my 6br kit to work with a mag extender. I used some epoxy putty to take up the space in the mag extender, and I also added some material to the end of the follower, as this is an accurate mag that doesn’t have a front plate in it. I then just filed it to fine tune. Works pretty good (ymmv)! Still considering trimming a spring leaf....
The extender:
The follower:
Done with this:
The extender:
The follower:
Done with this: