One consideration: Assuming you're using two depth sensors, you'll want to position them to get the most complete view of the performer on the stool. So, you probably want to avoid placing one sensor in front and one in back because the stool is probably going to interfere with more of the legs. It might be more effective to place the sensors to the sides, probably favoring the front a little more than back.
BTW, at the following link, there's a pic of me using a drummer's throne to capture motion for an Asylum 'SyFy' movie I freelanced on years ago:
Fake Airborne MocapI did this to create 'digital stunt doubles' of actors being 'launched from a natural water slide into a cavern'. Using iPi Mocap Studio, I was able to quickly animate the five actors for the sequence. Ordinarily, I wouldn't have had time for this because these movies are made very cheaply and quickly, and hand-animating the rigs would have taken way too much of my time.
I think the movie was called Age of Ice 2? Something like that. I'll see if I can dig up some demo footage for the sequence when I have time.
(Note: Any 'snowy' footage you see on my 2015 reel is from the movie, but unfortunately the footage I just described isn't on that reel. However, iPi Mocap Studio was used in some of the other shots on that reel.)