So I got me a 1.5 mm (~1/16") sheet matal, drilled and filed quite a bit...
Here I have a custom fit picatinny rail or alternatively a QD mount for the Beretta 1301.
With 1.5mm the spring powered pin isstill protruding enough so that the ratcheting system is still working and will keep the mag tube in place.
If any one wants details or measurements to make one... let me know.