Yes, and yes it is a lot of work. Not nearly so dicey as making tents, though. The latest project is motivated by the weight savings to be gained by using 0.67 oz. nylon from a group buy on this site, using panty hose material for the baffles so the outer shell can float freely around the inner, and the chance to experiment with some synthetic fills inserted into baffled compartments instead of down, only with larger compartments and less baffles than the finest down bags have. The goal is a one pound bag that is good to freezing before wearing the puffy stuff to bed. It is rewarding to make your own gear, but that alone would not make it worth it for me if I could not hope for some serious weight savings for the same amount of warmth.
P.S. To install baffles, I first sew pleats on the baffle lines on the width of both the inner and outer shell. The pleats are about a quarter inch wide, and so they reduce the size of the shells. So I do not mark the outer seam borders on the shells until the pleats are done. The inner bag shell is not as wide, so there will be what they call, differential cut. With the pleats, there is no stitching exposed on the outside of the shell to wear out, and the added weight is negligible.
Then the shells are folded at the first pleat line so only the pleat being worked on is closest to the edge of the work table, and the rest of each shell is folded back and away from the pleat on the work table. Then the baffle is pinned to the pleats and sewn. Then the shells are refolded so the next pair of pleats are presented for pinning and sewing the next baffle. A pro sewer would not have to pin. Sigh. The baffle seams are long, about 3 1/2 feet near the bag bottom, and over 5 feet at the top. The shells are not perfectly flat, as there are two short seams in them near the bag top to give the finished product a mummy shape. Sorry, should have taken a photo of a 1:10 scale shell pattern piece, but too late for that now. Maybe will post one later.
Anyway, the point of the P.S. is that it is not terribly difficult to sew baffles. I'm sure Roger's article will help if you decide it's a go. Haven't tried, and frankly do not fully comprehend the Karo system, so can't say if it is easier, but only note that the photos on the hammock forum look like true box baffled quilts, while some of the other photos do not, and appear more to be sewn thru, with more fabric allowance on one shell - they once did this on Kelty jackets, and it works better than a plain sewn-thru, but is hardly a weight-saver. Good luck!