Tinkering with some things today. I found the shells would squeeze into a plastic 12ga shell holder quite snug so i ordered up some cheap ones to mess with. Right now i am planing to plate mount the shell holder and bolt the plate to the mag in a spot with some beef. I will sort that out soon. Just to give you an idea:
The shell holder can be loaded in all locations. The top, foremost shell rubs the stock some but i think once it is plate mounted it will clear. It feels a little strange to reach under and around for shells, i may cut off the top 2 shell holders and just run the 3 lower ones so it is ambidextrous. The shells feel much better in these with one in front and back, i dont see then coming out accidentally unless dragged across something very firmly. These are just cheap ATI universal mounts that fit their top folding shotgun stocks. They could also be trimmed some laterally to slim them up a bit. I may try that, i have 2 to mess with.