FX Crown question?

Two that come to mind are the valve pin/valve seat and the way the barrel is secured in the receiver. My Crown is a first generation with the smaller diameter valve pin/valve seat configuration. The newer Crowns have a 6.8 mm valve pin and matching seat, I think 6.35 mm? My barrel is secured with two grub screws, and I think the newer ones use four. The power plenum question is a tricky one, as there doesn't seem to be a convenient place to add one. I remember someone posting some pics of a small plenum that screwed into the receiver between the trigger assembly and the regulator, but I've not seen any follow up on that.

James