CrossfireX and Video Card Flexing

So the other day while playing Battlefield I noticed my top card was making kind of a grinding noise, or the noise you typically hear when a sleeved cable is brushing against a fan. I popped open the lid of the case and slightly raised the top card...since then I haven't heard the noise and it went away completely. The two cards flex quite a bit because of the large coolers attached to them (Dirt 3 HD 6950s). Is their something I can put between the cards to prevent any possible contact that would be safe? Or is their anything I can attach to my case to stabilize the two cards and keep them straight and not flexed?

I assume the manufacturer expected this and it wouldn't be a problem but you never know. Is it bad for the cards to be slightly flexed while installed?

Some flex is OK (my 4870 flexed like crazy with an HR-03GT), but too much is bad news.
Fortunately I was able to reattach the backplate on my 6950 with the AXP, so this one doesn't flex anywhere near the level of the old card.

I used zipties for stabilizing the 4870, so try that. Anything between the cards would probably press down on the lowest card, so grab some ties at your local auto parts store instead.