I'm shopping around for a sling vest. I use a small over the shoulder zip container of my own design now that I can fit a fly box and some leader in but need a little bit larger to hold a sandwich and a light rain shell but not too big. I have seen guys using these sling packs and they look perfect for Spey casting with good unobstructed motion of both arms. Anyone have a pack that they really like? I just can't use a vest in the warmer weather.