If you plan to flip the system, you are going to have the hood issue regardless if they are paired & sized correctly as it is designed to be left/right with the zippers between (thus one person 45, one person 20 in your post), not top/bottom with the zippers on the sides (one temp on top, one temp on bottom).
"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover." - Mark Twain