I recently ran sims of the presence circuits from F and 3 CH. I also tried 250k for gits and shiggles. The greater the value, the higher it peaks out and the less sensitive the taper is. Some results are on the blog. 250k would jump once the pot begins to move, would mostly top after midway and would be really sensitive; a chunk of the taper is wasted. 100k is an overall better balance from what I recall and 50k is great for a person who doesn't need 1:1 gain on the control.