I drilled my RIA 1911 for the Cheely SRO mount, 5 hole pattern using my Harbor Freight mini mill. I have DROs rigged up, so it was super easy. As long as you have your mill, vice, and whatnot set up right, it is just fine for it from what I can tell.
But then again, I'm a total hack, so take my experience for what it's worth.