I built a game cart some years ago, but have only used it on one elk, and several deer. It works well, if the country is amenable to its use, and two guys are on it, one on each end. We used to plan to drag them out whole when I was younger, and we somehow got that done. I can't figure out how we did it now. The last several years (with one exception, where the cow was shot above a road, and I was able to get a rope around her neck and drag her fairly easily across the bunny-hill-sloped snow to the truck), it's been the gutless method in the field, two guys, 2-3 trips apiece to get the hide and meat to the ATV, then sewing the quarters and odds and ends into the hide and dragging the whole package behind the ATV to the truck.
My brother, with whom I nearly always hunt elk, uses a frame pack very similar to the OP's and was purchased from Cabelas, and I use a sturdy day pack that will hold an elk hind quarter in the main pocket, which I also secure to the top of the pack. I've thought about getting a frame pack, but the day pack works well enough. It is an Alps Outdoors, but I don't recall the model.
Getting elk out seems more intimidating that it used to. I'd love to have pack animals eventually. We'll see.
