bivysack.com
Should be okay for long bags. It is the same
floorspace as the first Chouinard Mids but
slightly taller, so should be a touch more
useable floor space. Also it is very roomy side to side
so you can also sleep at an angle if the terrain
warrants it.
Alpine Skills International uses this size for their
trans sierra high route ski trips and by digging in the
snow, sleep 4.
Same size too as the one made for Roman on the Alaska
thruhike.