The pic above shows the AT mountain plates. At first I was going to fab these up from scratch but they are very heavy duty and worth it and in my opinion the best possible solution for mounting of the bags. I also got all of this done in 1 day at my usual slow/double check everything pace so it saved a lot of time by having them. Again, big props to AT and how awesome these guys (and their products) are...
Here is it bent/mocked up. The photo shows my friend Ray who is a professional welder for a big structural fabricator who happened to show up yesterday afternoon (and is a hell of a guy). He suggested using spreading the weight to reduce flexing. That is the only issue with this mounting is the M416 frame is about 1/8" (so quite thin so it flexes).
You can see the strap that spaces out the mountain point of the upper bracket (which is going to take the brunt of upward motion). So it is crucial that it gets spread out and is strong as nails. Second, you can see the lower mountain point which is just more 2x2 box tube cut in half. Works excellently and is also strong and nice and easy to mount/apply as well...
Ray from Arches welding:
Fully mocked up:
You can see it all tacked up: