Spent yesterday dialing a 5° recline and 12 mm edge radius into a flax/PP composite shell, and the way it breathes and micro‑flexes is the closest I’ve felt to a mesh chair without fabric. If you’ve lived with natural fiber shells, how’s the lumbar spring after a year of daily sits — any creep or does the curve hold?
I’ve been on a flax/PP shell I pressed last year; the lumbar took a tiny set in the first month (about 2 mm) then stayed put. My one tip: “pre‑bias the lumbar” in the tool by 2–3 mm so the settled curve lands where you want; if you’re at 5°, shoot for about 5.8° initially. What’s your fiber orientation through the lumbar band (I ran 0/±45 with a slightly heavier 0)?
Seconding @nina_b85’s “pre-bias” note — what worked for me is laying a 60–70 mm UD flax tape doubler across the inside at L4-L5 during the press to shift strain off the curve; it nearly kills the first-month set but makes the lumbar a hair stiffer… What layup are you running in that band?