I use a Granite Gear cuben sack with an eVent bottom for my Feathered Friends bag. Very lightweight, very "stuffable", very waterproof. But also fragile, I put a small slit in it while stuffing the stuffed sack w/bag in it, into my pack. Which reminds me, I need to get some cuben tape and repair it.
But... On my last Uintas BP trip this summer, I did not use a stuff sack for my sleeping bag. Since switching to a smaller, lighter backpack (ULA Circuit), I found the "soft rock" of a stuff sack not very packable (hence the slit) and also not to carry very comfortably. So, last trip, I simply put my sleeping bag in a plastic trash compactor bag in the bottom of my pack, with no attempt at compression or stuffing. Then stuffed my gear in on top of it, forcing it to just fill in the cracks and spaces. Made my backpack seem more roomy and also made it more comfortable to carry.
Long winded way of saying - I think the GG cuben/eVent stuff sacks are awesome, but I no longer use any kind of stuff sack for my sleeping bag when backpacking.
BTW... I use Zpacks cuben bags for all my other bagging needs - food bag, ditty bag, clothes bag etc. All are Zpacks cuben.
To get back to sleeping bags... I'm going to probalby get a WM Megalite for BP'ing next summer. My FF Swift is just too warm (20* bag) and at 2 lb's, I can save some weight by going to a 30* bag. Love my FF bag in general, am only going WM just to try something else. Have tried to warm up to the quilt idea, the weight savings are just so attractive. I'm a thrasher and a cold sleeper though, and just can't quite take the leap of faith and go quilt. Will revisit and reconsider a Zpacks bag vs. the WM before actual purchase in a few months though.
- DAA