My first pattern-ship was an Aurora with a OS pumped 61. I started with an old VF but quickly moved to a new 61 long stroke and then replaced the piston and liner with the "Hanno" piston and liner. Same rpm and power as the "Hanno", it just didn't have a red head.
It has been the benchmark for me on reliability, ease of use etc.
I own and run other motors but if I can afford it I will always go for an OS.

Cheers
Michael