I did a little experimenting today. Standard size hollowfill pillows ($2 at wal mart) fit just about right in the Clark pockets. They snug right up to each other leaving no gaps. Looked like it would be very effective at low temps but prob overkill in the 40's & 50's. I did cut a couple in half and they opened the pockets up nicely for dead air space but left some gaps so as hopefully not to bake me like a biscuit.
This is pretty bulky and only suitable for car camping but I think it will work real well. Going camping with the scouts this weekend and hopefully it will be cold enough to put it to the test. If so I will report back here.