I do not like the mounting bar clamps...they bend and loosen up. I put aluminum pads under mine -- use blind nuts or
another set of pads on opposite side of engine bearers.

        Russ, I can't comment on the ARC because I don't own one and haven't seen one. The ARF has steel inserts buried in the mounts. I used  brass threaded inserts buried flush within the bearer itself which was epoxied in. I happened to hit one of these but didn't damage the bearer. Luckily I  didn't drill the front one first due to it made the hole walk slightly. I've seen the clamps in use but they seemed to always appear to be bending. I don't think I would trust that application. Ken

I had no problem with the aluminum pieces, but I did have one of the inserts pull out, which loosened the clamp. This was a drag of course. Especially when you are putting on the your personal best flight ever (and at a big contest!).

This was from the first ARF/ARC run, so it is possible that the problem was fixed. In my case, the inserts were just glued in and not threaded (as I recall). They seemed to be put in from the outboard side of the fuse, so the constant tension of the mounting system just made the glue let go. If they had been put in on the inboard side so there would be some plywood bearing against the insert, that might have helped.

Before it happened, it worked great. Not so much after!