I didn't like how much M4 mag adapters moved in my Jag Scattergun, so I designed this one to lock into the bottom of the receiver much more securely using 4 M3 screws. Requires 4 5.5mm square x 2.5mm M3 square nuts, 4 M3x10 flat head screws, and this M4 mag release and spring:

https://www.evike.com/products/54146/

7 walls and 30% infill should be enough. Feed port and mag well walls should be solid.