As a buddy use to say 'Lose an ounce a day'.. it all adds up.Light construction techniques....I'll be following this, for sure.
I met a gentleman who focused on light weight when he was building his plane. "Reduced Hex" nuts were used throughout his build. They might make some uneasy on applications where bolt/nuts are used in tension, but I certainly can't see anything wrong with them for bolts used for shear loads. Hex Nut Lightweight Reduced Dimension On Wicks Aircraft Supply
He also used aluminum washers in place of steel washers. Grams....no doubt, but in the end they all add up and contribute to the number on the scales.