Back in 1995 I opted for FF to make my Vireo and Hyperion option (as I suggested in the other thread). I also opted for the Volant Hood as well. I opted for the combination in eVENT rather than Epic so my set-up is heavier. I upgraded everything to 800+ down and increased the Vireo by 2oz of 800+ overfill. I have the shorter Vireo (62" because I am only 5'6"). I also had FF put the flange on the Hyperion and snaps on the Hyperion, Volant Hood, and the Vireo. That way the Volant Hood can be used alone or snapped on either the Vireo or the Hyperion Jacket.
By the way if you did not see, FF offers a 15% discount if you purchase a Vireo at the same time as a FF jacket; the discount applies to both pieces so it is a substantial savings. The savings applies to any upgrades in fabric, down, and overfill.
My 62" FF eVENT Vireo with the 2oz overfill weighs 22.4oz; the L FF eVENT Hyperion Jacket weighs 16.4oz; and the eVENT FF Volant Hood weighs 3.4oz. Those weights include the appropriate flange and snaps.
Be aware that the Hyperion Jacket is a bit small and designed to fit like a Fleece sweater so if you want to use much additional clothing you may want to size up one size. With the Volant Hood, the jacket will be much warmer than without.
I like the set-up very much but have not used it that much. It is quite flexible. You may also find the Vireo a little tight for size, but if you read Ryan Jordan's Spotlight review of the Vireo, he indicates if it fits you well it is one of the best lightweight down options. It fits me fine including usage with the Hyperion Jacket with or without the Volant Hood.
If you want the system even lighter, ask FF about the new Nano option which would make the set-up lighter than the Epic. That I am sure will require that FF make the order from the ground up, but it may well be what you want.
By the way, due to the design and length and need for a warmer jacket, the Nunatak Arc AT and the Skaha Plus will not be nearly as flexible or as warm as the FF Vireo, Hyperion, and Volant Hood combination. The FF Hyperion (or other lighter vest or jacket) would be worn inside of the Vireo. Heavier jackets would fit outside. The Vireo has more down in the lower and foot box portion of the sleeping bag. The upper portion adds warmth that you can adjust by different size/loft jackets inside and out. The FF option has more fabric and down than the Nunatak option.