20 years on the board here, from Chile.
Always felt the board size should be related to your height and shoe size.
Big dudes, big boards; small shoes, small board and so on
I'm 6 feet tall, US 9 shoe
always skated 7.75 as kid
got into 8.0 around 5 years ago, mainly cause you couldn´t find smaller boards here (the good ones of course)
been using 8.1 and US 9 NewBalance 868's for 1 1/2 years, my flatground its on point on this setup
tried bigger boards (8.25) a few times but can't make 360 flips or my classic flat game, same happens when I skate on slim shoes (adidas adiease or vans)