Congratulations, you're a sensible human being who has figured out that listening to your body and intuition works much better than all these "optimal" solutions everyone is chasing after. I've suspected for a long time that much of ergonomics is just snake oil and hardly based on any evidence at all. If sitting upright or in some specific allegedly ergonomic position is making me feel tense and wears me out, how is that helpful? I prefer to go with what millions of years of evolution have coded in me. Fortunately I don't have a desk job anymore so it's not of much concern to me.