My grills use the Lee Valley 0.375" diameter by 0.1" thick rare earth magnets (www.leevalley.com) and 7/16" diameter x 0.1" thick magnets (Hobby Lobby). My grills on the arrays that you saw are 6' high by 10.5" wide. They are designed to rest on the base of the array so I'm getting some relief from gravity. The enclosure has 8 concealed 0.375" magnets in each baffle. Four of these are in the corners and these while the others are equally spaced along the baffle long edges.

Now I use a lightweight aluminum frame material (0.75" wide by 5/16" thick from Lowe's or Home Depot) with plastic corner connectors. In each plastic corner of the frame I glue a stack of two 7/16". The polarity of these magnets are of course attractive to the ones in the baffle so that they hold the frame to the enclosure. Finally, along the long sides of the frame I tape thin steel washers to the underside of the frame so that you get some attraction so that the frame does not sag away from the baffle along these long sides.

Let me hear if you need more info.

Jim