Liners VS Bivy

[seanBLAMMO]

I own a Seek Outside Silex. I like it so far. However, I've only used it elevated so far with 6 inches or so of gap between it and the ground. I know on colder/windy days I'm gonna drop it right down, but I am tall enough that touching the sides will be an inevitably. I'm in the market for a bivy for this purpose. I also own a Cimarron, for which I am considering buying liners.

I'm interested in other's experience with bivy's and if buying the liner is still worth it if I have a bivy. Lightweight bivy recommendations are appreciated. I am considering a Borah bivy with added fabric at the head end. Thank you in advance.