Not OP but for anyone else looking for a heavy duty chair, I got this one about 4 years ago that holds 450+
I've lost a lot of weight since then but I can attest it can comfortably hold the max weight :)
I'm 6' 10" and ~350 lbs. This is the chair I've been using for about two years now. Not the prettiest chair around but worked for me, especially for the price I paid.
I have had one of these for a while now and it is a good chair, very sturdy and well made.
So I use this chair at work since 2015 and like it.
https://www.amazon.com/gp/product/B00658O3JU/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
They don't sell it direct through Amazon anymore but maybe there is a newer model?