Retro/ULT mod-what "EXACTLY" needs to be done?

[trxtr]

OK, I just recieved my retro valve and it takes my mag into a whole 'nother ballpark from my classic, as most of you know. I want to install the ULT (which I already have), I know Brad at Paintball MAX does the drill-out mod, I've already corresponded with him and it'll cost me twice as much to ship my valve there and back than it will for him to mill it. I have access to my college machine shop and wanted to know what "exactly" (bit sizes, drill depths, etc.)is entailed in this mod, so I can do it my self.

thanx
trxtr