I mounted a steel plate between engine stand-offs and eng. mount ears and bolted lead bars to them.By moving the mount point forward it reduced weight reguired by 6oz.. This was on a TF F4U ARF. If you mount weight in the cowl lip the vibration will break down the cowl at the mount holes or mount ring glue joint.I have tried this and that was the result.It takes a while but it will sooner or later.