They work great for pronghorn. Just keep the rear closed so movement inside the blind is not back lighted in any way. Cookie uses an older pop up for her photo runs, and has had animals within 5 yards and some times so close even just the head would not fit into the frame. Suggest putting them in a couple days before and maybe out in the last third of ones effective range. Takes some time before they are willing to tuck in tight against something new on the landscape. Crittrgittr's comment about wind is on point. With Cookie's unit and wind, I think the game is more disturbed by noise than movement. Grass, shrubs, and trees all exhibit movement in the wind, and game is not in panic mode for the duration. I have used camo burlap, which moves a fair bit, but does not rattle like the tightly stretched nylon versions.
Another hint - with early morning and evening efforts, one seems almost invisible if he can simply sit in the shade of a juniper tree or some other natural structure. Move out into sunlight, however, and they'll be on to you like stink on a skunk. Also, if one can walk in and out in the dark, they don't seem to do well with the earliest of light. Cookie has often hit her blind in the dark and had animals bedded inside of 100 yds when the sun makes it up.
Good luck,