Upside down American Flags aren't all that glamorous to me.
Your guitar's made of wood. Even covered in polyester finish, it's going to move with the weather. It won't swell or shrink anywhere near as much as some, because the polyester seals any moisture out- but it also seals moisture IN too, so there's nowhere for it to evaporate out of the woods. What this results in is a slight swelling when you play it for long periods due to heat from the friction from your hands and fingers, followed by a slight shrinkage soon after you stop playing. So, the neck's going to move a little or a lot depending on how hot the surface will get. Though humidity doesn't play as STRONG a role, it's still important ,and temperature and amount of light will, also. Pay attention to th etemperature fo the surface on the front and back of the neck, it's a good clue.
Best suggestion? You want to set it up when it's most likely going to be in the same condition it'll be in when you play it. If you're gigging 45 minutes at a time, play the thing for 10 minutes, then tweak it, then play it for another 10-20 minutes and see where it goes. If you're a couch player, you might have to do a little more compromising, but even couch players can play 45 minutes to an hour at a time and the neck will get warmer. So you be the judge- if it's going to be a workhorse, work it before you tweak it, because it needs to get loose , to be in fighting condition, before you can get it right on.
