If you are not dead set on a chest pack, you should consider a lumbar or hip pack. Placement of the pack on your hip or lumbar after a long day of hiking and casting will be appreciated, trust me! Maneuverability is greatly increased and i think you will notice that the location of a chest pack can really be quite cumbersome when it comes to fishing, especially on longer drifts, and/or high sticking. I really like my Simms Headwaters Guide. Access to the contents is in my opinion superior with a hip pack, and with the headwaters guide specifically, the open front of the pack doubles as a work surface on the water. it is much easier to work at waste height than chest height (think about where your arms are going to be more comfortable)!
I have owned both chest and hip packs, as well as vests, technical and traditional. This hip pack is by far my favorite.