I'm one of those guys Mr. Glavin mentioned who has the Mustang 50 version as sold by Byron's. I bought a Fuji 50 muffler from tower for it a couple of weeks ago, it turns a 20x8 Zinger at 7,200 rpm, I just received a ProZinger 18x10 in the mail today, several guys suggested that this is a better choice of a prop. I'll find out in a day or two. I haven't been able to flip start it yet but it starts instantly with my Miller 4 to 1 reduction on a Hobbico 180 starter. It runs fairly smoothly. It has very low time on it maybe 1.5 hours. I believe Byron's and Fuji both have the bore and stroke figures reversed on Tower's website and in the Mustang 50 manual. My measurements tell me that it has the same bore as a Zenoah G45 and a slightly longer stroke. giving it 2.84 cu. in. displacement vs. the G45's 2.76. I know you only asked about the Fuji 50 so the G45 info is free.