This may or may not be of help. Years ago I had a 4870 which was pretty heavy, I ran it in the top slot for like three years on an MSI board. When I took it apart to sell the board, I tested it lying flat, and it would not boot in the slot closest to the CPU, even though, in the case it would boot fine. I think over time the PCIE slot came loose between fan vibration and weight and would only work with that weight on it. It was the only card I had in my PC, and the other 3 slots booted fine with it flat. When I sold the board on eBay, I explained this very carefully, the board worked still, but would only boot in one position, with perhaps only a heavy card (didn't have a light card to test it), the board still sold, and it actually went for like 60$ more than my original BIN was. I'd find a way to support the card, even though it will probably be fine for all intents and purposes.