RE: 1.20 AX
So here's the report.
I did order a new engine mount and get it drilled to fit the 1.20 AX and the cowl. Changing the cowl engine cutout from the .91 FX to the 1.20 AX was not difficult and I still have a nice fit. The carb fits perfectly in the old carb openings and hole in the cowl to reach the .91 low speed needle was nicely lined up on the AX. Of course I did need a new needle valve hole but no problem. Personally I don't care much for the angled needle but I know others that do.
As for the muffler, I don't much care for the "Power Box" design. The biggest part of the change over was ripping out the chin of the plane to fit the large width of the muffler. It also is heavy. The weight comparisions available online don't include the muffler weight difference, this would have been good information to have ahead of time as I could have planned for the required battery move.
The engine was installed in a .90 size pattern plane that I've flown almost every weekend for the last 4 years. The 1.20 AX has given it a new life! I tried about 6 or 7 different props and and the APC 15x8 seems just about right for my application. I was always happy with this plane but the new combination is incredible. Slightly faster in level flight and tons of grunt in the verticals. My maneuvers are just massive now.
I knew I'd like the extra power and I was right. I still think that the phrase "bolt right where where the .91 used to be" is a might of an overstatement but the results are great. As I said before, I still would have bought the engine and done the work but had I known that the engine required a different mount I could have ordered the mount ahead of time and had everything on hand when I started the job. Instead I tore the entire plane down and found that it wouldn't fit. I had to reassemble to fly that weekend, order and wait for parts, then repeat the job with they arrived.
OS, A+ on the engine but C- on the advertising. We really have come to expect better from you.