Nice looking benches. 2 things to be aware of with your new benches.
1. Try to remember to turn trees regularly. Light is stronger at the front and weaker at the rear where blocked by the slats so branches will be weaker at the back if not rotated regularly. Can be compounded depending on orientation to the sun.
2. Lower shelves have even less light. Shaded from the rear and from above. Use lower shelf for shade loving trees and developing stock that won't mind too much.