My partner and I and doing a project for class. Our first idea wasn't seen as too good of an idea. We've gotten ideas about using air cooling. We've also had people mention their backs getting overheated under a hydration pack. Our idea is some type of riser that will keep a Camelbak or other type of hydration back an inch or so above your back. That way, air can get through to cool your back under the hydration pack. I'd appreciate it if you could answer a few questions about our problem.
Do you where a Camelbak or other hydration pack?
If so, how big/how much water does it hold?
Do you find that your back gets hot under the pack?
Would you like a way to let air to go under the pack?
Would you pay $15 for something like this?