My first trainer had a S-61 in it. The instructor set the needles and it needed no further adjustment for the duration of training. Put the supertigre in you plane, either the ringed or ABC engine, they are both very good. These engines are some of the best deals going in the .61 class.
I own several OS .61's, and they are nice. But I fly the ST's more and expect they will last longer than OS.