I’d suspect you’re still going to have heat problems there no matter what you do. If the air around the unit gets warm, moving that warm air in+out of a Stevenson screen isn’t going to make it any cooler.
Suggest finding a place that is ‘really’ in the shade, or alternately going the Stevenson screen route in a relatively shady place that won’t catch radiant heat if the fence next to it gets hot due to sunlight etc.
I had the same problem with the overhang by my front door. It’s always warm up high where there’s no insulation in the overhang, so the morning’s sun warms it up and it stays warm up high. Not enough airflow there regardless of temperature.
I built a cheapo bird-box type enclosure with scrap wood and painted it white and put it outside on the other side of the house where it stays shady the longest til at least noon or later, and have had no problems since.