I found a way to drop the temperature of the MSI 7950's by about 10° C. If you are like me and unable to get a hold of any PCIe risers then this a good way to get multiple cards sitting next to each other without overheating.
I'm using the MSI 990fxa-gd65 with 3 x MSI 7950's with each connected directly to the board without any spacing in between and running them at under 70° C each. This is using GUIMiner with the GPU defaults set to 7950 high usage. I get 570-580 k/h per card with default afterburner settings.
Disclaimer: While doing the following does not void your warranty, doing anything with your card could damage it and I can't be liable for that. Be careful, and don't do things you're not comfortable with.
The way to do this is pretty simple, just remove the mounting bracket on each card.
What you'll need: Small pair of pliers, Phillips screwdriver (both a small and medium preferably), plastic zip-lock bag
Step 1: Remove the pins next to the DVI port. Use the pair of pliers to gently loosen the pins and then remove them the rest of the way by hand.
Step 2: Depending on your model you will either have two or three screws on the front. Using the small Phillips screwdriver remove the two screws at the top and the third screw above the HDMI port if you have one there.
Step 3: Using the medium sized Phillips screwdriver remove one final screw on the inside of the bracket near the top where the cross fire ports are.
Step 4: Slide the bracket off and put the bracket along with the screws in the zip-lock bag.
That's it, now your cards will be able to dissipate a lot more heat! For increased cooling if you are using an open case design (e.g., milk crates) then you can now point your fan at the back side of the cards (opposite the end with the display ports) and the air will be pushed through the heatsink and exhaust out the side with the ports.
If I can figure out how to easily post pictures I will. If you have questions just let me know!
If you haven't already done it, you should tilt your computer. Tilt it to the side and you'll notice your GPU temps falling by 5-10°C.