Radials can flat spot even overnight in the driveway... but they drive back out in a mile or two and are nothing like the old bias plys were. It is a somewhat common new car complaint, and seldom mentioned after warranty unless new tires were just installed.I don’t think radial tires get flat spots just make sure they’re inflated properly, it’s only 4 or 5 months for crying out loud!
Why do you need to fill the gas tank completely? Asking because I don't know, not to argue.
Every tank will get some condensation, you are right on target... but I wanted to add that ethanol fuels tend to both absorb water and evaporate the ethanol, causing a tank of somewhat crappy gas after a while... if more extreme, the fuel may separate and be garbage.If the garage goes through heat/cool cycles it can cause condensation in the tank, less metal exposed with a full tank. Of course if the temp is fairly stable, not a huge deal.
I would try to fill with non-ethanol if possible, and consider draining the tank as an alternative for long storage. $5 hand operated pump and a gas can... fresh fuel should make up for any additional condensation.