I spent a LOT of time trying to figure out a method behind the madness of calculating how much down goes into each compartment. One thing I did was make several “pillows” of various widths (1” to 6” wide x 20” long), which approximated a jacket compartment’s dimensions, and then started filling them up until they seemed to achieve the right density. I then weighing them so I knew how much down went in each one.

As a reference, I used my Feathered Friends down jackets and tried to achieve a density equal to them. They know what they’re doing!

Then I calculated the theoretical amount of down for that compartment (based on a cube) as well as the additional amount of “overstuff” that was needed to get where I got, (ie, the density equal to my Feathered Friends jackets).

I found that filling just to the theoretical cubic volume (ie, length x height x width) was nowhere near enough; it definitely needed “overstuff”. The question was how much. It ended up being between 50% and 100% “overstuff”. I put that in quotes because it’s not really “overstuffed”; it’s really just the percentage increase from the cubic volume of that compartment.

I ended up using a lot more down than I was planning but I feel that it is correctly stuffed. In fact, some of the compartments could have used a little more down to avoid migration.

I used 11.94 ounces of 850 FP down. This approximates the Feathered Friends Volante, though that jacket is different in that it has a box construction vs sewn-through.

My kitchen food scale is not really precise enough to weigh down, so I bought a very accurate (and inexpensive) scale that measures to the thousandth of an ounce. It rounds up or down at the thousandth place but this is precise enough for down. You get readings as precise as 0.240 or 0.245. If you need 0.243, you could just round up to 0.245.

The scale I bought is the AWS LS-1000 and it cost $30. It also comes with calibration weights, which usually you have to buy separately (and they are surprisingly expensive). This scale even comes with an AC adapter. Note: it has a 32 ounce max.

http://www.awscales.com/compact-bench-scales/178-lb-1000-compact-bowl-scale

http://www.amazon.com/American-Weigh-LB-1000-Compact-Removable/dp/B002SVQHWY

Incidentally, the method I found very successful for stuffing the down was with chopsticks. The smooth lacquer-finished ones worked best. You can pick up small or large clumps of down, and there seems to be more static electricity on the chopsticks than skin, so it is attracted to the chopsticks vs your hand. And the ripstop seems to have more static electricity than the chopsticks, so in the same way, it seemed to stick the ripstop more than the chopsticks.

To weigh the down, I made a box with heavyweight aluminum and weighed the down after taring for the box. I transferred the down from the bag it came in to the tared box so I could get exactly the right amount of down. Once it was weighed, I could take the box off the scale and transfer the down to the jacket compartment.

It was much easier and neater than I’d imagined. While there was a bit of vacuuming to do at the end - some of the tiny clusters are just going to float away no matter how careful you are - I had no mishaps.