Emma,
I just bought a Mystery Ranch Golf Mahal Pack. This is an expensive Pack, but an amazing weight distribution through the yoke system, comfort, unsurpassed quality of material and craftsmanship, and the ability to collapse the pack down to hold 15-19 discs including putters or expand to hold almost 40 discs. If your willing to spend $150 on a Dual Pack, $180 on a Grip, or $200 on a Simian. Then you might consider $250 for a Yoke harness system that is a dream to carry a heavy load from a company that has proven quality and knowledge of outdoor packs in a versatile design. Umbrella setup is cool too (doubt I will use much though), and fully waterproof with built in rain-fly.
http://www.mysteryranch.com/s.nl/sc.11/category.104719/.f
http://www.dgcoursereview.com/forums/showthread.php?t=32090&page=20
http://www.mysteryrants.com/category/disc-golf/
I really value my back, since I only get one. My loaded PDGA bag with Innova straps has taken a toll on my spine this season. This Mahal could help me play without pain on those grueling dual 27 hole layout rounds in the Summer at Milo as I try to get as good as the people I admire. They have 3-different sizes to fit any frame, and the yoke is adjustable within each size frame.