I have Kifaru packs and MR packs. The Tri-Zip design will old up and work just fine, ESP. for your uses. They use the Tri-zip on the 3 day assault military packs among others; and they hold up to that use and the dusty environs they are used in.
I have a MR Sweetpea pack ( in the OD / foliage color) and although I have not used it for a hunting day pack yet, I have no doubt it hold hold up fine. Would not carry real heavy loads of meat in it, but for day pack use it would be fine. The pack would hold up fine, but the suspension is designed for only about 40 lbs with the live wing optional waistbelt (which I would get). I have used my pack for day hikes and snowshoe and ski day trips. I have also used it as a carry on pack. I really like the pack and I think it is fairly priced and very well made. I like the lack of busy internal pockets on MR's recreation packs when compared to the busy internal pockets on the hunting/ military line. The outside stick it pocket on the sweet pea is another nice feature.
Pack should work well for your purposes. I know it has for what I have used it for. And I would not hesitate to use it has a close in hunting day pack; where you could get a pack frame if need be after taking a small first load of meat.
