hey david, if you're going to be putting your down or your blackbird (both of which i own and care for dearly) then i just have to make you aware of the possible impact to your gear. if you smush down in a compression sack or even synthetic fills for hta matter, you ruin the loft. over time. i have the compression sack available for sale, but if me and you have the same gear down and a blackbird, there's a reason i dont use this unless its winter time and i'm putting socks and layers in it.
let me know if you really want it man, but just know that putting down inside of a compression sack is not a good idea. its much better for you to stuff in a large stuff pack and then smush it into you pack so that it fills the space in your pack better and helps distribute weight better too.