I hope you mean milling the SLIDE Adam.
And Happy, I've never known a rds to REPLACE the integrity of a milled slide. The material is gone, plugging the hole with an optic doesn't make it as strong as it once was. That being said, milling a slide doesn't significantly weaken a Glock slide.
"You find it offensive? Well I find it funny. That's why I'm happier than you."