Charlie, very nice work. I like a 24-25-26" spread depending on the length of the rod. I don't care so much about the length of the upper and lower cork.
I am more concerned with the position of the reel seat and whether it is uplock (< 14' rod) or downlock (> 14'). A 14' rod splits the difference. I prefer to favor balance by positioning the reel properly in the first place, not by adding extra weight with rubber or wood grips if it can be avoided.
I have reamed premade corks with care (can be done), then added 1 or 2 rubberized rings at the bottom and top of each section for looks, durability, and more length. Anglers Workshop sells some pretty fat stock grips (I like them fat). I made a lathe setup with my hand drill and a threaded rod, but my shop is stuffed with bicycles and a driftboat (no room to work!), and the lathe setup works only ok, not great. Hard to get it 100% perfectly in the round when spinning at high speeds.
How are you guys turning the big grips on the blank itself?