Still no 'official' support for these features, but it can be forced without too much fuss. Just use this little guide here:   http://forum.warthunder.com/index.php?/topic/115531-enabling-sli-and-crossfire-support/
 
As usual, back up the file before you edit it. I'm using 2x 7970's and got a 40% framerate boost after enabling my Crossfire. Pretty slick. Apparently they're planning officially supporting it, but we'll see.

As an additional plus, the multi-monitor support is now near-perfect.  Correct FOV, AR, and the HUD elements have been placed correctly. _b   Gotta love how a smaller studio can get this 95% correct, yet billion-dollar franchises still drag their feet on it, even though the technology has been at the consumer-level for a decade.