These look very "airy" which is great for outdoors and keeping comfortable. The increased slope on the back seems like a worthwhile adjustment to try.
When I sit in a chair with a more vertical back, I tend to slide forward a bit it the seat is too "slick". Do you find that an issue with the front-to-back lacing in the seat? Crosswise would give a bit more grip or even a full cross lacing of the seats. Given your comments about the rotting dowels, I'd pay attention to the feet where they contact the ground. A dip in some thin epoxy would seal up the end grain and help out there.
Looking good! Chairs are one of those items that make me hesitate building with all the curves and need for ergonomics. Takes skills to get it all right.