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.
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...ask for the old paths, where is the good way, and walk therein... (Jeremiah)