Thought this might be of interest. I wanted a QD Sling mount on the butt stock of my SUB-2000. I used the Micro Flush QD Sling Mount from Impact Weapons Components (QD Flush Mount)
and some hardware from the hobby shop where I work.
It seems to be very solid. The stiffer plate on the backside is brass. It is a bit shiny in the photo because the paint is still wet. It dried to a matte finish.
I am pleased with the result.