Okay, that looks pretty straight forward as the "knob" for adjusting the thermostat, I'd leave it just the way it is. Very similar to texasgal's Allen wrench adaption.
The wing nut is a great addition, so it can't be accidently turned above your chosen temp. Set the temp, stabilize it and tighten the wingnut to hold it in place. Most of the controls are very sensitive, so only make tiny adjustments. Even with the knob I have to really look to see if I've moved it at all.
The only odd part for me? Clockwise lowers the temp, counter-clockwise raises it. Just something to get used to.