Hello Thorns!
Just read my way down all this thread. Looks like Buff sans visor is indeed the way to go to keep ears and neck out of the sun. For the face an additional cap might have to come into play though...
To extend this topic beyond the head: we're heading Andes-way and thinking about sun-cover strategy. While expecting a fair bit of cloud cover, that makes matters worse in a way because the light is coming from all directions rather than just one. And the altitude makes things worse again. A year ago in Africa we got fried. Heads not so much as we were wearing brimmed hats (no helmets then, but come to our senses - were just rebelling against compulsory Australian helmet laws), which indeed have the severe downside of suddenly covering your face when going downhill and looking sideways...but hands and legs were a pain. Legs: never again going with short shorts. Days on end in equatorial sun at 2000m (Kenya, Tanzania) means that the top of the knee/ lower quad is the perfect solar panel. Going for all 3/4 length pants for that reason. My partner had real issues with sun burn on calves as once the sun is past say 3pm you get a solid side roasting (heading south/north) with no shade from the bike whatsoever. We slapped on sunscreen, but the only thing that saved us was the Malawi rainy season kicking in (which is still deceptively sun-burny, but at least concentrated illumination is reduced).
The body part we had the oddest sunburns with (no, not there...) was our hands! We were both wearing fingerless cycling mittens, which meant that the end of the fingers were out all day. Despite sunscreen slopping, sweat just washes it off after a while. We both got burnt under (!!!) our fingernails, bizarre I tell you, needless to say painful. I made some make-shift covers out of hairties & squares of material (one hair tie around the wrist, one twice around middle and ring finger), which limited further pain, but where practically a bit limited and looked like we were about to brake out into some tribal dance...
So: for sun-burn central riding, what do you do for your hands? Long summer cycling gloves? Fingerless mittens and then thinner ones on top? We'll have to prepare for both tropical as well as cold/ altitude/ bad weather conditions, but I'm trying to minimise 'stuff'. So our current thoughts are long summer cycling gloves (for padding, had cyclists palsy - weeks of numbness between little and ring finger- from initially going without cycling gloves), merino liner gloves and water/wind-proof MTB-y gloves. Your thoughts?