K.O., thanks for your comments. I had heard nothing but positive comments about the Saito line, and I was upset with O.S. for the remote needle on their 2 strokes and so I bought the 150 for my Cap 232. Runs great. Then I bought a Twist and the Saito .72. It also runs great. My brother in law has a Saito 100 GK and it runs great. We both started to break in our Saito 100's together on an outdoor bench setup. We had the same balanced APC prop, and the same setup. From the start, his ran smoothly my non/GK Saito had an awful time just to keep running. I checked the gaps and they were right on. I still persisted trying to run it and the vibration was so great that the carb broke off the backplate. I was disappointed as I used to compete and haven't had a bad engine since the YS people tried to introduce their .61 longstroke.
I called Horizon and they were very nice and eventually they sent me a new engine.
Several months have passed and I thought I would break in the new Saito on my UCD .46. I took it out to the field and had identical problems. The vibration was so bad that the axles enlarged the outside holes of my wheel pants. I could also hear a click when I rotated the prop with the glow plug out. I traced it down to the port side rocker arm striking the valve stem, but the starboard side made no noise at all. I have no idea if this is normal or not.
I called Horizon and asked if they have been having problems with the 100's and they said no, and I told them I had a letter D stamped on the mounting flange.
They are sending me a mailing label to return the engine.
I think my problem is unusual, and they have no way of knowing whether I'm mentally deranged or not. My doctor doesn't know either.
Let me make an off topic remark about you wanting larger planes. I went through the same route and I was surprised to find that the larger planes are so much easier to fly that I went back to the smaller planes, .60 size. A great thing about this hobby is that there is something in it for anyone at every level of skill. To quote a famous author, "Cadilacs are not for everyone. Some folks also like Lincolns."