I've used the Hyde mounts with and without the noserings. They work extremely well in isolating the airframe from the vibration. I would not build a pattern plane without one. Pricey though, And if you need a nose ring the cowl needs to be strong enough to hold the nose ring no bolt on cowl.

Hyde does have some firm idle mounts that are a lot less money, these can be used without a nose ring. and at quite a bit of cost savings.

Another thing to remember about the hyde mounts is they are usually set at 6 1/8" or 6 3/8" from the thrust washer to the firewall.