We have our 2015 38FLSA parked in the sun for most of the day, it gets shade in the late afternoon hours.
During our spell of hot weather (94-98, with 60-80% humidity) we maintained 74 inside without issues.
I do run both units, and keep the bedroom unit 3F cooler than the front unit. Our living area is comfortable when the shades are drawn. (we pull both shades in the heavy sunlight)
Ours is working perfectly if I use both units in the heavy sunlight.
2015 Sierra Denali 3500HD SRW
2015 Jayco 38FLSA - Loaded -
B&W Companion 20K slider hitch