Seems to work fine for me on my 2x 6950's
and your temps are still 72? Mine are 69 for a 6970 at 880/780. It doesn't really look like that underclocking is working to me.
Yeah, the case is closed (with 2x120mm fans on the side) in my basement which is about 85F ambient right now (I live in PA, hella heat wave!)
Usually they sit lower than that