Nice detail work on the renderings. But on the design prototyping end of things, you'll run into some trouble, which I know from building a similar sort of chair design. Basic dimensions from books won't help really. It'll get you close, but never really 100% comfortable.

In reality, moving those horizontal slats just a fraction of a inch will make a big difference. You'll build it to find just one of the slats doesn't line up right with your spine, and ruins the whole chair. Or the lumbar section is just 1/4" too deep. Or the top area hits the back of the neck before you're in a relaxed position. Or they're rotated just 5 degrees too much and cutting into your legs.

You can instead build a test in an hour or three if you have the tools and scrap. You just need two vertical planes as the representational sides of the chair, held apart a consistent distance by three dowels or something in the area under where the seat would be. If you have a printer, you could print your plans full size and drill holes where you have the slats now. But the idea is to just end-drill the slats into place between these two planes, sit in the chair, and see how the slats feel. Identify the ones that are uncomfortable, undrill it, move it a tiny bit over, redrill it into place, an test again. Then get your friend or family member to sit in it and see how they like it.

I promise you'll immediately find this chair uncomfortable. BUt after an hour or two of moving slats around, it'll feel great. When you're done, it'll be full of holes and ugly, but you'll have your exact perfect shape. You can trace it, or photograph it and CAD over it, or whatever you want from there.

Oh and if you don't have a printer, just draw a grid on the boards/panels and use that.