What you cold do is drill a hole through the back strap and frame and insert a T-nut and screw through the back strap. I would go as small as possible if you do that.
As to the rattle, many of my double stack mags rattle at various points of loading. Even some of my 1911 mags rattle a little.
As to the rattle, many of my double stack mags rattle at various points of loading. Even some of my 1911 mags rattle a little.