Thanks for your responses.
I've heard about sagging with the Gigabyte because it's so big and heavy. Would that be a problem with SLI? I wouldn't be going for the g1 edition with a backplate because it's like $30-40 more per GPU.
They are pretty heavy but no that should not be a big concern, just make sure you tighten the screw heads that holds it on the back plate of the chassis...