RE: Frustrated with Covering
Too many people "depend" upon the shrinking qualities of the material when installing. It is important to pull the material taut before tacking it down and then you don't have to shrink it as far. I live here in Memphis which is just as hot as you and leave my planes in the car for weeks at a time and never get a wrinkle. I use Monokote and admit to never using another brand as I have no problems with it.
Have you seen MinnFlyers videos? You're probably past that point but there may be something to learn.