First update on having CZC mill my OD green P01 for the 407k. I was hoping/expecting they could mill the slide for the optic in front of the rear iron sight. I've seen pix of one P01 slide milled by CGW that accomplished this. I emailed CZC asking if they could do the same. They said they could try. I figured it was worth a shot since sending the slide off to CGW would mean a very long wait for its return. It's been my experience that CZC's turnaround time is far quicker than CGW and they both do exceptional work. Anyway, CZC rec'd the slide a couple weeks ago. Yesterday I rec'd an email from Stuart letting me know that the guys at the shop weren't confident they could mill the slide without the cut slicing into the dovetail cut or ejection port. Stuart sent a photo of the slide marked for milling and it did indeed look very, very close. Stuart gave me the option of going ahead with the cut or going in another direction. We emailed back and forth a couple times. I ultimately decided to have them mill out the dovetail and install the Holosun since the tiny Holosun has rear "sight blades" built in to it and Stuart said they co-witness OK with 5.5-6mm front sights. I asked that they replace the front sight sight with an appropriate one if the already installed Dawson FO sight doesn't work well with the Holosun. Thanks to Stuart for the timely emails and advice. Stay tuned for further updates as I have them.