I have a couple Gen 2's set up, one dedicated to Large Frame, and one set up for small frame.

I have had very good looking success using my Porter Cable PCE6430. I use older mills to make the first few cuts, and as already mentioned, I decide how much of a bite I take, less is faster. I switch to a new end mill for the trigger cut. That is the only thing I have ever had chatter when milling, and it makes an ugly trigger slot that has to be hand filed.