I'm not a fan of slats in pergolas, as they tent to sag with time, as walls yes they work great.
This is what I plan on making for my set up, with dual shades... a 70% and a 30% on opposite sides.
View attachment 540760
Or build two pergolas side to side and have one with 70% for JMs and other delicate trees, and the other one with 30% for more hardy trees that can't tolerate 100 degree full sun days here in central Texas. I saw a similar set up being used in one of Bjorn videos of Kouka en. You can see the wires on the pic below.
View attachment 540758