Items to complete this project

Metal 10mm x 75mm x 2.5mm with 2 mounting holes
Neodymium magnet 60mm x 13.5mm x 5mm with mounting holes

This is what I used, modified the bracket to work
https://www.amazon.ca/gp/product/B077NW365K/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

File or Dremel screw heads for smooth surface, you need to make the magnet and metal surface to be flat as possible

4 x 3/8 Wood screws from HD BC#2241202155
Trim the screws for the lid

Super Glue to reinforce everything

4-40 x 11/16" Pan head screw, for ramp

Exalt Speed feed Gate
https://exaltpaintball.com/exalt-universal-feedgate-v3-black/

Take your MCS Box Mag apart, transfer the bottom bearing over
Its a tight fit, but everything fits without modifications

Enjoy

RD Fabrications