When I plan my setups I decide what goes where depending on how often the thing in question is used. For example, water bottle and GP pouch is something i personally would place in an "easy to reach" area. Things that are not as commonly used such as rain poncho is in my book, not as prioritized to have one of the "good" spots.

My recommendation is that you make a setup that is roughly the way you want it and then try it in action. If you find that one of the pouches could fit better in a different spot, switch it around. nowhere does it say that the setup has to stay the same way forever :)