Theres really no set specs to follow and thats the great thing. It will be your custom pack and you build it how you want. Just tell him the max weight you expect to carry. My pack is a heavy beast, over 7,000 cu inches, tough and for 120+ pound loads. That made the weight go up to 8 pounds and I am fine with that. It is a pack bulit for true 120+ loads, comparable only to an external. Other dual stay packs claim they can carry this load but seeing how the frame on his critical mass packs is built I beg to differ.
He also offers a lot of fabric choices. I am no expert on that but 500d cordura is a good cheaper option. Full spectra is a bit lighter and I think tougher but will raise the price of your pack by a lot. Dyneema grid is an even lighter option and is also a tough fabric but for a hunting pack I would choose Spectra or cordura over it. You can even chose the width of your shoulder harness and other things. If you go to his shop and try on some packs you will get a better idea on what its all about.
Your best bet is just to talk it over with him and he will guide you toward the choices you should make. Take a long look at his website and see what base design interests you.
After I have some time with my new pack I will do a full write on the details and its performance.
