Just curious, has anyone ever converted their CZ 550 Magnum to a blind magazine, ie. via a McMillan Stock and Williams Universal Trigger guard? If so, what did it entail and how much weight was saved?

I can't answer your question, but I want to add that I think blind magazines in a DG rifle are a bad idea. Jams in a controlled round feed rifle are much easier and quicker to clear when you can open the floorplate. I know, I know, they shouldn't jam in the first place but Murphy's Law is still in effect.