I watched my tiny-tach and it confirmed my seat-of-pants/hearing input that I was turning rather more revs at a steady 35mph than with stock weights, when I went lighter.
I didn't want to rev my engine for no reason - (my stock acceleration was fine for my needs) so went heavier with the Dr P's.
I do recall that I dropped more than 500 rpm's when riding at 80 on my Burgman 400. Do not recall - but it may have been 1,000 fewer! It used to do 8,000 at 80mph, stock rollers - dropped to 7,000 at 80mph with Dr. P's.
Stig