I think the 1.5 inch baffle height that appears in the Thru-hiker article is assuming that you sew in 1.5 inch baffles made from netting. It is not intended as a starting point for a sew through quilt design. For one, you will use less down, because your sew through baffles will be ellipsoidal, as opposed to (roughly) rectangular (in the case of the thru-hiker quilt). I have only modified a sew through bag into a quilt so far, so I cannot help you with fill calculations. The received wisdom is to overstuff by about 30% I believe. I did your calculation and got the same answer, so I don't know whats going on there really. 82 grams is clearly not enough. Suppose your shell weighs 150 grams, add 300 grams of down, you end up with a 450g quilt. That sounds about right for 45°. Whatever you do, remember to use a vacum cleaner, some cardboard tubes, and organza netting to handle the down. Do not attempt to stuff the bag by hand!!! You load up a tube with down, put it in the baffle, hold down the material around the tube and blow. For what it's worth, I think sew through is a good idea for a warm weather quilt, as it saves alot of weight. I added velcro tabs to my quilt, so I can attatch my down jacket (also with tabs added) to the top. This helps reduce cold spots, add warmth, and means my jacket doesn't keep slipping of during the night.