I recently did a 520 converson using a DID 520VM chain, Renthal ultra lite front sprocket and Sprocket Specialist hard anodized aluminum rear sprocket. The total weight saving over stock was 2lbs 2ozs. Most of the savings was from the rear sprocket. I think the difference in chain weight was about 8 ozs. I don't know why a 520 chain would be any less susceptable to rust.