I have seen a few boats out this way with painted spars. We don't get the super high temps that you do, of course.

If I were in your situation, I'd pick up a phone and call a mast manufacturer (Hall spars, etc.) for advice. Whomever you call, be sure that they have experience with customers in your environment.

Hopefully you can stay with a marine product. That would be expensive enough, I'd hate to think what "aviation" on a label does to the price!

I wouldn't talk to a paint company or worse, a marine store, until you talk to someone who's actually used the product in that environment.

Hope this helps.

Mike