Found reviews of people that used it on Sappire 4850s and they say it works.
Newegg says the 5850 is 1.5 inches tall (38.1 mm) and that cooler says its 30mm tall, so I can safely assume it will allow you to crossfire. Found some reviews as well.
As for the all copper, if you are going to reuse the cooler Id get it, otherwise just save your money. It dosent seem to perform that much better or worse.