I'm using metal mounts on two of my airplanes right now. never had a problem with breakage or screws coming out. OS and saito make mounts for their engines with pre-drilled and tapped holes. Tatone made metal mounts and they are still around as do J'tec. The weight difference between a metal mount and a plastic/ fiberglass mount is negligible. If your plane can't handle the weight you need a bigger engine. A lot bigger.