Yes, 3000cui is a lot. His Gortex shell doesn't pack as well as Microlite. Plus the weight and bulk of 700 fill doesn't compress as well as 850fill. The standard stuff sack(XL) that comes with a Kodiak(long) is 1145cui. Many folks who carry a lot of down use bigger packs to avoid compressing more than necessary, thus his bag has lasted many years of stuffing.
...ask for the old paths, where is the good way, and walk therein... (Jeremiah)