hi David,
my remark should not be a criticism to you or your build nor your age as I¡®m at nearly the same age. I built and repaired several of these tuners and recognised a difference between applied power and displayed power. Root cause was the 11th turn on the binocular core. Even ready built ones from china have nearly all 11 turns!!!! So my remark only should help you to get an even better result. nothing more!
Best 73, Immo
Immo, DL5KB