Wonderful job, lots of satisfaction in doing a bit of craftsmanship on such a personal project as a pack. It will serve you well in the next fifty some odd years. Then your heirs will get a lot of use out of it too.
Load a 40-50 lb. bag of dog food into that pack, then adjust the tump & pack straps, so that when you lean forward, into the tump it takes the weight off the shoulders. Walk around with just the tump to train your neck muscles, when one bag of dog food is no longer enough, add another. Don’t try to do the training period on a canoe trip. You might do this in the neighborhood after dark, so the folks don’t think you’re goofy. When I was young and tougher than I am now, I used to portage a 17 foot aluminum canoes and a full Duluth Pack on mile long portages in the Boundary Waters & Quetico Park without a needing a rest. My tripping companion would portage the other heavier Duluth Pack, axe in one hand & cook kit in the other. Paddles and fishing rods were stowed and secured in the canoe. We could travel a long way in short order.
While in college I lived five blocks from Lake Bemidji, I would portage to the lake a couple nights a week, spring and fall quarters, for a paddle in the dark, just to keep in canoeing shape. On Friday nights same thing only would just keep paddling to go up or down the Mississippi River for the weekend.
One summer I had a good paying summer job, I bought a light weight Grumman canoe, l could not believe how much difference 15 pounds made in portage ease.