Fasten the rubber feed pan to a 2.5' x 2.5' piece of plywood and fasten a hanging ring to one corner or along one side. You can then hang it and it will be 'flip proof' when lying on the floor of the stall.
I was actually thinking about drilling holes in the rubber and using leather strips similar to shoe laces on one side. So far I haven't had any "flipping" problems but you never know. Thanks for your comments. Keep'em coming!