Some extreme video cards in the studio with 3 fans and 11″ card length can pressure the bracket and slot leading to the card sagging a bit in the typical tower chassis.
The R9 Fury is a huge card. It has 3 Sapphire fans which are replicable. The card is slightly larger than 2 slots. The GPU can draw as much as 300W of power when playing demanding games.
The HD 6970 came originally with a blower fan but it was refurbished with the Arctic 3 fan cooler. This card is another power pig at close to 275W of power.
The card length is driven more by the three fans than the radiator or the logic board.
The R9 Fury does stay fairly firmly in the slot. The HD 6970 was heavier but it held in place fine with no issues. Both cards are a tad loose in the slot but they are secure enough for gaming purposes.
There is not much that can be done to minimize sag. A wooden pole from the floor of the chassis with a small wood top can secure the card if the sag is noticaly not level. A fishing line from the top of the machine can also provide some support. Not much else comes to mind for coping with heavy video cards.