I did a couple of these for me and ma youngling.... although the last few meets, I've been using both on my hammock and leaving him with dad and the central heating
I chopped off the 'hat' (and made it into a hat, tis verrrrry snuggly round the fire before bed! ) (Thread is at
http://www.bushcraftuk.com/forum/showthread.php?t=81692 ) and the leftover shoulder bungee was left on to tighten the end. I removed the zip, took the opening to the end, seamed a bungee carrying sleeve in and created a circle of bungee that sits in the carabinas both ends- They hold the edges high up the sides which is handy in wind and it can be slid up the bungees so it sits neatly round the shoulders.
Now I've learned to use em effectively I'm delighted but I don't walk far so am not weight focussed
I do find they can pick up spray mist on wet windy nights, dunno if that would compromise a down filling....