Even without all the particulars weighed and measured, your points are well taken.
My default plan with this current build is to dip down to 170mm from my usual 172.5mm crank length. I imagine that I won’t be able to sense the difference, especially because I’ll experience the new bike and new crank arm length as one new complete system, instead of doing an A/B test of different crank lengths on the same bike.
Just as an aside, when I mentioned shorter crank arm length to my frame builder, to see if he may want to consider a slight tweak in geometry, he vigorously cautioned against shortening crank arm length, but I take that as the normal expected reaction until this area gets studied more rigorously.
I guess when it comes down to it, I’m wondering if there are any shorter crank arm experimenters out there who would advise me against going shorter, considering that I’m not a racer or TT guy, and have lots of climbing on most of my rides…?