I have older Dana Designs Terraplane 80, which is the same bag, but different frame. It works well and did a lot of backpacking with it. It looks like the Terraframe 80 is no longer in stock but it still has the 65 and 50 3-zip (I think that was the one you were referring to). I didn't know that they featured the load carrying option!
I just bought a Mystery Ranch Glacier from Sierra Trading Post a couple seasons ago for $150...it does NOT have the load carrying option like the Terraframe. I wish it did.
I would recommend any of the Mystery Ranch packs, and I'm positive that it would work well for hunting.