You have a lot of experience, but I have to quibble with two things.

One, your shoulders don't have to suffer under a pack.  Thick and wide straps are of course helpful, but even moreso is a wide and snug waist belt, along with a properly positioned and adjusted sternum strap.  Transfer 30-40% of the pack weight to your hips and your shoulders will forever thank you.

There are two downsides to the hip belt.  One is that it tends to pull your pants down.  Tighten your belt.  The other is that it tends to make your gluteus medius muscles work overtime.  Let 'em - they'll get stronger.

Two, you can counterbalance some of the back pack weight with a front pack.  It doesn't have to be big, and you don't have to carry it high.  I've found that a 15# daypack does a nice job opposite a 50# back pack.  I extend the straps so it rides low, and my forward and downward view is essentially unobstructed.  There's no need for a third leg unless navigating really rough terrain.