I do not understand why you would have problems with the sun.
Junipers are NOT shade plants and prefer full sun.
Guys it depends.
The practical truth is that any potted plant can suffer, eventually die, in tropical sun.
I've lost much more trees in the summer here than in the winter, including tropicals and a juniper.
When the "label instructions" says "full sun, at least six hours a day", that means temperate climates, OR...3 hours early morning sun, three hours late afternoon sun.
Six hours in full sun from 10a.m. to 4 p.m. here in the summer will be fatal for many bonsai, even watering twice a day (as some really go dormant, you can even overwater them).
Just my practical experience.