Some other things to ponder when an air-cooled engine is running too hot:
Is all of your engine tin in place? I see it all the time at car shows where the engine compartment seals are missing, tin has been left off etc. One serious offender is the tin at the front of the engine ( against the "hump") missing. This does not improve cooling it instead allows you to vacuum road dirt and garbage off of the street - a great disservice to your engine. A guy I know up here had a chronically overheating engine. This tin piece was missing and that handy oil wiping rag which he kept under the engine cover had been sucked into the cooling fan along with a shopping bag ! I yoinked all of that crap out of there and he replaced the tin. Voila - a happy engine. What are you using for oil? In the heat you experience down there, 30W-50 would be advised and I would lean toward removal of the thermostat altogether and wiring open the lever for the cooling louvres. This is a subject which gets kicked around a lot. My experience, and this is Southern Ontario, Canada with a summer only driven car, is that if you do a patient driveway warm up at idle, a thermostat is not needed.
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.