Seems everyone & their brother has been asking this lately, so I'll go ahead & give the LONG answer into my thoughts on the issue:
VERY rarely are magnets alone good enough, no matter what the strength is. I personally wouldn't trust ANY of my props to magnets alone, they could fall off your back or leg & get broken (ask Master Groves what happened to his 7ft light rifle sometime -shudders at the thought-). Also, YES, it looks cool to reach back & pop the thing off your back to pose for a picture, but think how easy it would be for someone else to do the same thing in a crowd & now you're out a prop that you put a couple hundred hours of work into or worse, several hundred dollars, personally, I'm not risking that, no matter HOW cool it looks. Magnets work great as a secondary attachment option, but I HIGHLY recommend something a little more secure ESPECIALLY at a con.
When it comes time to do mine, I plan on using a keyhole faster & a post screw. What's a keyhole fastener? Think of those chain/slide lock things on the inside of the door at your house, but a keyhole fastener is only about 2in long. My plan is to put the post screw (a.k.a. Chicago Screw) on the back of my armor near my shoulder & then glue the keyhole faster to my gun near the stock somewhere, then VERY strong neodium magnets will then be used to hold the front of the gun at the correct angle on my back. Chances are, I won't be able to get the thing on/off my back without assistance, but then again, neither will anyone else.
The magnet thing is simply an immature dream, any REAL costumer will tell you to think twice about using magnets alone.
Hope this helps!
