Using sun-screen mesh on Harrisia jusbertii

[Lair3514]

I've moved H. jusbertii around in my yard but I can't find a spot where they have ideal conditions. They are currently along the north side of house which puts them in shade in winter and full sun in summer. The summer sun is stressing some of them which I suspect may turn yellow if I don't do something.

Tucson Cactus & Succulent Society puts H. jusbertii in this sunlight category

B - PARTIAL SHADE - Species which require some protection from prolonged hot sun, but which will tolerate about a half-day of full summer sun. Often these species prefer morning sun and afternoon shade.

I have some sun-screen mesh. Is it okay to just drape it over the plants or should it have some support to raise it above the plants?

For ""summer" watering, I started at about 1/2 gallon per plant every 3 weeks and will go to every 2 weeks as temps go into 90s. If there is anyone in Tucson or like zone, does that sound about right? This will be their second full summer in the ground.