Bumpers: Metal Edging To Retain Cloth Needed ?

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Historically we used to put 3/4 x 3/4 x 1/8 L along the bottom edge and top edge of our bumpers, screwed into the back with the L onto the top and bottom to help "lock" the cloth in place. Recently we just did the top. Now we would like to not bother at all (good overlapped seam stapling with an air stapler).

Just looking for a little reassurance that other teams are quite successfully using bumpers without any special mechanical cloth "clamping" system like our L aluminum edging ?