After months of saving and research, I've finally made my first down under-quilt, and just in time for the cold winter too! I pretty much followed the detailed instructions of the under-quilt design from http://www.instructables.com/id/Down-Hammock-Underquilt-Ultralight-20F/
. At the end, the quilt weighed a little over a pound and a half with a temperature rating of around 15*F. I even had enough material left over to make a few stuff sacks and a compression bag. Total time, including down stuffing time, was about 30 hours of work.
As for the materials I purchased, they are all of HIGH quality and at very reasonable prices (pretty much unbeatable from what I found).