Sweeney,
At 73, I understand the aging process. I remember "Pulling an all nighter," prepping for a test, now I brag about pulling an "All dayer," that is a day w/o a nap.
I think if you build a true Verner rifle with a 40 cal. 42-44" ( A) weight barrel you will be amazed at how easy it carries....of course you would not want to tackle big game with it. You are harvesting some beautiful wood there and are lucky that you can get someone to cut it for you. I once cleaned a half dozen walnut butt logs w/ root balls and took them to the mill. I got a flat refusal, and had to saw off the root ball before they would cut them...