Jamie - glad you decided to share my MYOG impulsiveness! M50 is very expensive, and perhaps the price will come down a bit this spring. The thing is, I live in Minnesota and even though I do some winter trips and a lot of cross country skiing, it is dark and cold outside and definitely prime gear making season. I elected not to wait until April, May or later to get a jump on this project. I've been making enough of my own gear that I'm now able to sell off some comercial/cottage made gear I previously used to fund new projects.
I made an M90 quilt from Thru-hikers kit last year, and used the full 12 oz of down. I later converted this to a top bag, which I prefer, with a ~30 inch zip and an extra single later strip of momentum on bottom for a minimal weight penalty and better draft protection. The final product is a little less than 22 oz and has plenty of room to spare for my 6' frame. Along with adequate CCF pads and a Whitney down parka (six oz of down, 13.5 ounces total), I've taken this down to 14 degrees F and been comfortable. Basically, when combined with some other clothing I can count on this set-up for lows in the teens. For cold but not frigid temps I think the combo of a warm but light parka with a top bag or quilt is pretty tough to beat weight- and function- wise.
Making a similar top-bag with 8 ounces of down and M50 and also making a cocoon-style hooded synthetic parka might leave me with my ideal set-up for most conditions with lows about 30F:
Night time lows in teens or twenties: M90 topbag (22 oz) + Whitney Parka (13.5 oz) = 35.5 ounces.
Lows in thirties or more: M50 top bag (15 oz) + synthetic parka (8.5 oz?) = 23.5 ounces.
Part of me thinks I should stop being such a geek and just use the set-up I already have:) One reason I'm not is that my fiance comes with on most trips and she would love to inherit my original (warmer) top bag when I'm not using it.
So anyway, thats my thought process regarding how to use the kit I ordered. I'm excited to see what everyone is able to do now that lighter fabrics are available. Also, time will tell just how M50 performs compared with time tested fabrics like M90.
If it were me, I'd say a quilt with 6 oz of down could be sewn through, but if you are going to try to make a light 3-season quilt with 8+ ounces of down go with baffles: it seems you go very light and push your insulation to relatively cold temps and those baffles would be appreciated when the temps drop a little lower than expected. The ability to completely customize projects like this and make exactly what you want (for a fraction of what you'd pay from a cottage shop) is my favorite thing about MYOG.
Keep us posted (as you always do!).