A big name college professor tried in earnest a few years back to prove that the logging industry was wasting way to much hardwood (the ratio for softwood is like 80% of the tree-hardwood is like 50%). Anyway he tried special kiln techniques, special sawing techniques and after a year or two of study concluded that the limbs just don't make for good lumber. I forgot where I read this, but its a well known study.
I know first hand Popil is only good on the first few butt logs. We were sawing a popil top into boards and the tree pinched so tight from internal stresses that it stalled the sawmill. Now this was a 327 Chevy engine driving a 1901 52 inch rotary sawblade. To stall something like that just by pinching to pieces of wood together is quite the pressure.
Last year I harvested a Maple on my own property. The tree was straight, growing on flat ground, and showed no signs of any stress at all. Just the perfect soft maple tree. When I went to saw it on the bandsaw sawmill, the boards that popped off it were odd. They peeled off in the banana shape. 3/4 on each end and 3 inches deep in the middle. No signs of stress, but man did it ever have some in it.
You just never know when you cut into a tree what it will give you.
I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"