That barrel extender is going to look great, I think. For me, it gives it just the right length to look more balanced. I like all the 416 lengths I've see, but I find the short barrel makes it look a bit too stubby for my taste, and the long barrel makes it look too unbalanced, because of the short RIS rather than the long handguard of an M16. But that mid-length barrel looks just right. And with the matching length inner barrel will give it that little extra boost in accuracy at ranges.
I was originally just going to buy this 416 as a collection piece, but now I want to use it. At game time I'm gonna be really torn when it comes to choosing which gun I want to use. lol