Well I tweaked with the texture bandwidth buffer and bufferpool size in the fsx.cfg file and have it running very nicely now, even at max settings - I couldn't believe the improvement, can fly over LAX now and it's very smooth. The Mustang still taxes it a bit, but certainly playable.
I saw some photos of the icing but haven't tried it yet, will have to give it a shot, very cool feature. I wish all the airplanes would show ice accumulation.