I agree. Getting them to the ground where they can stay cool from the coolness of the earth can help, as well as the increased air flow. Also, adding an additional dark blue or green tarp over that white billboard tarp may help increase the shade potential in that hoop coop, while getting the sides up for more air flow will help as well. I use push in stakes for electric fencing to keep my flaps up and provide more shade potential beside the coop. Using the blue/green heavy duty tarp was an incredible difference from when I used a brown/silver tarp on the hoop coop....much, much more shade produced from those colors for some reason.
This pic shows the tarp and the stakes that raise the flaps for me....seems to work better at putting shade into the coop than rolling up the sides, as the sun can boil in there when those sides are merely rolled upwards.

This pic shows the tarp and the stakes that raise the flaps for me....seems to work better at putting shade into the coop than rolling up the sides, as the sun can boil in there when those sides are merely rolled upwards.