I understand the fill power rating on down. Some bags I've been looking at recently say 70% or 80% down clusters. I assume that this means the remaining 20-30% are down "shake," not clusters, but still down? Would this have a large effect on the insulative properties? I'm guessing it would, but how much? A 650 down bag with 80% clusters vs. a 800 down bag with 70% clusters? Or, are the two connect: 650 means that there is some shake. 800 means there is practically no shake, all clusters? Is there really no way to tell, except experience?
Any thoughts?