One more solution...
You don't necessarily have to use the Tru-turn adapter. I picked up the spinner nut adapter for Moki 2.10 for the Dave Brown spinners and it works fine with the big Tru-turn spinner (3.5 in. P-51 on my Pitts M12). The Dave Brown adapter does not require counter-drilling the prop. You just ream the prop 10mm for the Moki prop shaft, balance it and you're done. I use the step reamer (sounds like the same one you have) in a drill press and just go slow. It gives a perfectly centered hole every time.
Here's a link to Chief Aircraft. They carry the correct 10mm X 1mm adapter (both long and xtra long) for the Moki 210. Tower does not. I used the long adapter on the Pitts.
http://www.chiefaircraft.com/Models/Model.html
Click the "Accessories" section then "Dave Brown Spinners and Adapters".