I have used the metal mounts that come with ARFs and found that they will hold well. Like others have said, I would not use on much more than a 46 engine. I don't like the hard plastic mounts that now come with many arf kits simply because I find they are difficult to get adjusted and can allow the engine to move around thus possibly getting into the cowling. Nothing worse than getting your cowling cut and mounted only to have the engine shift even a little. Then it's hard to get back into the exact same position.

I usually use O.S. engines and really like the O.S. aluminum engine mounts that come already tapped for the specific engine you are using. They are light weight and the engine is mounted securely with machine Allen heads and no clamps. Just add a drop of blue lock tight into each hole and you have a very secure mount. Yes, this is additional cost, but in the end you get what you pay for.

Just my 2 cents. No doubt you will get multiple opinions on this topic.