In my JD-3520-Cab with the AC going, its generally one of my John Deere ball caps as I use a big set of earmuff headphones for my MP-3 music, . . but all the rest of the time its a Cowboy hat for me. Light one for summer, heavy one for the winter and of course a "good" one for "dress,..or Honky-tonkin" nights! BUT, I'm never without a hat of some sort.
Another thing: for guys with high foreheads, we tend to sweat a lot. Like "Woodchuckie" above, I cut a face cloth in half and sewed it in front to soak up the sweat as that "terrycloth" material is great for that!!
CHEERS !
. . tug