Hello folks, it's been a while...
Sun protection is a big deal for me for my head and the rest of my body. I've been having good luck with hats from Outback Trading Co. I like the flat, wide brims of the Aussie-style hats (I don't keep them snapped up on one side, though), and make sure they have the chin string in case a weird side wind comes through the car and tries to take away your hat. I haven't lost one yet, but the wind has tested my hats a few times. A brim width of 2.75" and wider all around is a must for me. Sometimes I'll even tip the hat down to the sunny side just to make sure it covers my side neck area. Their hats are moderately priced and will last for many seasons.
Outback Western Hat Collection - Outback Trading Company
A few months ago I bought two of their hats to replace versions I bought back in 2017 when I bought my Spider. The model 14851 Harvest Breeze (in the lighter khaki tan "wheat" color) for top down driving, and the model 14721 Holly Hill (darker brown color) for non-driving, inclement weather wear in both rain and snow. They are both size XL, but the Harvest Breeze runs a tad larger for fit than the Holly Hill. Check their sizing charts and return policy for sizing issues. I use very thin foam, 1/8 - 3/16" thick, behind areas of the sweat band to improve the fit of the Harvest Breeze. Strips of cloth will do the same thing.
Harvest Breeze-
Harvest Breeze | Mesh Outdoor Hats by Outback Trading Company
Holly Hill-
Holly Hill | Canyonland Hats by Outback Trading Company
I also own a Tilley hat, but the hat is very light and flexible (crushable), so the brim flaps around in the wind of driving, and generally Tilley brims are not wide enough for my needs.
Premium brands Stetson and Akubra (Australian made fur felt hats) are beautiful, but flat brim styles come and go from Stetson, and Akubra will cost +$250, but both are worth looking at. Turned up cowboy hat brims offer less sun protection.
UPF +50 shirts (with tall collars) and pants are worth shopping for as well. Protect that skin from cancer, it's the only skin you get.