repeating what I've written in earlier threads ... but had to have an aeron for about 5years at work,
but after a herniated disk, privately bought a kneeling chair, varier balans which I still use daily 15 years later, look for a 2nd hand one
if you look up details on kneeling chairs, you can't slouch and the angle between thighs & back is opened up;
one of other dislikes I had for aeron, was rigid front edge behind the knee joints.
e: and another con was the mesh which was a bit cold both in the A/C office, and would also be in the less heated home office, and it's not very conformal to backside, versus padding
e2: V Ok the sayl has a padded seat too.