Instead of putting my inflatable pad in the pocket against my back, I used it to line the pack as shown in the attached Inflatable Pad Backpack Diagram. It provides rigidity and "splices" the joint between sleeping bag and other pack contents.
I stopped using a stuff sack for my down sleeping bag and just stuff it in the pack. This provides a lot of rigidity to the lower section. Its compressibility lets me use it as variable fill. If I need more space for other gear, I just compress it more. Once everything's in, I inflate the pad to attain the desired overall rigidity. The result is a very stiff, unified load which doesn't require stays or any external padding between the pack and my back.
--Submitted by Keith Selbo