I didn't read the whole thread, so forgive me if I'm repeating old info.
Many years ago, my dad helped me reroof (metal panels) my house. He told me to get white. (California heat.)
Not wanting to blind myself, I bought off-white, or an eggshell shade.
When he arrived, he told me to put my hand on a piece of white metal he had with him and one hand on the off-white that I'd purchased.
The off-white nearly burned my hand while the white was easy to touch.
All of that to say, have you considered using a white tarp for the roof to reflect the heat off the hoop house?
https://www.amazon.com/GUARD-SHIELD-Heavy-Purpose-Waterproof/dp/B0974KT55L/ref=sr_1_3?keywords=white+tarps&qid=1684632999&sr=8-3&th=1