yup down shifting is a problem. Some manufacturers like to try and sell it as a feature (you can shift to down to meet your insulation needs!) but I've met very few who have bought into its advantages. If I'm hot I stick a leg or an arm or my whole torso out the bag. When I'm cold I find out in the middle of the night (after temps have dropped) where I am in no state of mind to figure out how and where I need to shift down.

I have to believe baffles that allow down to shift are made that way for easy of manufacturing. I've never made a bag myself so it is all speculation.