Glock makes an extended mag release. I rounded the edges, which ended up mirroring the rounding of a Vickers release, with a dremel sanding drum and file. It's nice that it's only a $4 part.
http://www.glockmeister.com/Mag-Catc...uctinfo/G1981/
FWIW: When I removed the grooves from the GFA, I was getting a bit of "bite" from the enlarged area that surrounds the pin hole, it needed to be relieved as well.