I have a Goldberg Tiger 60 which is about the same size as your PT60 only low wing. I had an OS 61 SF pulling this plane around and it was just fine. I got it used from an estate sale of one of our members that had died. I got it cheap.. $25.00 US. But, the engine had a bad main bearing. It was not bad enough to not use the engine, but you could clearly hear it at times. So, I flew it for a while but eventually removed that engine in favor of a Super Tigre 75. This engine was fine, although it clearly was not the quality of the OS 61 SF. It leaked fuel because the needle valve fit was not that great. In the mean time, I picked up a replacement bearing for the OS.

Also, after a few flights, the internal parts of the muffler, the baffles, came loose and it made a ringing noise when the engine was running. I called Super Tigre reps and they sent me a new muffler right away. Great service. However, after a few flights, this muffler also came apart on the inside. When I called them back, they suggested that I install a tuned pipe, so I ordered a Macs pipe and header with extension and installed that. Well, the carb still leaked fuel a bit, but what a power house that engine turned out to be.

Soooo... you have two choices that are good ones. I do like my OS engines, I have 2 46's., one 50, one 61, and three 1.20 AX's. So, you can clearly see my preference. And if you get a Super Tigre 75 for instance and you have to go the route I did with the tuned pipe.. well, you will be right up there with the cost of the OS. Your choice, and you may not have the muffler problem that I did, they may have addressed that and fixed it. The fuel leak... well, it only makes a bit of a mess that is no more difficult to clean than the oil on the side of the fuselage and all over the wing and tail surface just like any other model engine.

Good luck with your choice. Hope the above information helps you make an intelligent decision.

DS.