Stepping up from 32mm to 40mm OBJ gets you 56% more lens area / light gathering ability, and if that little bit of weight hinders a person's hiking, they need to get into better shape.
You're a bit confused. An 8x42 has an exit pupil of 5.25mm... that's a 24% larger exit pupil than the 8x32's 4mm. Your "56%" surface area is a factually irrelevant red herring - the size of the exit pupil (ocular divided by power) and quality of the glass are what give optimal light transmission, not the size of the ocular per se. And quality glass goes right to the most important aspect of binoculars - the ability to resolve detail.
A 10x40 binocular has an exit pupil of 4mm - an 8x32 binocular has an exit pupil of 4mm. That's not "56% more light gathering ability," that's 0% if they're of equal glass (and BTW, binoculars don't "gather" light, they transmit light). The 10x40/42 are what most hunters are convinced they need to carry. Truth is, my little 8x32 Ultravids will be brighter than average built 10x42's just due to glass quality.
If I can't see it with the 8x32 Leica's I tote, it's not legal light. My only wish is my 8x32's were 7x32's.
I've hunted Alaska to Maine to here in Montana going back decades. All with 7x30/8x30/32 glass. I've never found the need for 40mm glass, though I do love Leica's 7x42BN and their 8x42 Noctivid (but not for backpack hunting - more for general wildlife viewing/birding). Even then, push to shove, I genuinely dislike the bulk and weight of 42mm bins.
As to "shape", I doubt very much you could keep up with me in the mountains, and based on your comments, I doubt you've ever done an actual wilderness backpack elk hunt (living for days in the backcountry out of only what you carry in your pack on your back).
But at least you're from Texas...
