I wear the 'Stich RC in wet, humid GA, and up to about 85* it is VERY comfy at speed, but has to come off quick when stopped. Strangely, mesh gear can be uncomfortable in desert hot conditions..too much moisture is sucked from the skin while riding. A full suit creates a "micro-environment" where your moisture loss can equalize-think of bedouins in their long robes..the long, light colored robes not only reflect the heat, but contain the body's moisture, just evaporating off enough to stay cool.
The 'Stich RC , with it's underarm vents and back vent open "inflates" at speed, to give you a kind of insulating barrier, and a constant rush of cooling air. I haven't tried the wet shirt trick, but my bro (who has less heat tolerance) does put ice in his front pockets to melt. Says it works amazingly well.
One of the local ST riders (Coleridge) got the cooling vest which is frozen, and then worn under gear....seems like a great idea in your area!
Another thumbs up for a 'Stich....my sis wears one, and took a pretty severe high side-flew about 15'..slid a few more. Walked away with a sprained wrist, and a bruise. The Aerostich was pretty much unhurt. (She took the MSF course the same day, to re-qualify for travel on her base. She was the only one who was dry in the course, since it rained the whole day)