Holy moly, I have a very similar chair but in red. I just got it so I could have a robust chair at bar-height.

My problem is that removing the footrest portion leaves mounting brackets poking out at whichever point you remove it. So I’m particularly interested in your process for chewing through any metal bits around there.

I don’t have trek-thematic advice, but I can tell you that little chrome armrest bit is the perfect size to rest a normal-sized trackball.