"Castle, Ron" wrote:

Paul,
  The engine mount needs the backplane of the firewall to make rigid the
engine mount. Rubber mounting at the firewall will cause a lost of strength.
The is a dangerous change. Most of these experimental aircraft require the
engine for cg. A lost of mount and engine is going to ruin your day. I would
not attempt this. Unless you're suicidal.

I think you are referring to the rubber bushing in the firewall mount.
We thought of that.
That would be true Ron if it were not for the four steel tubes connecting
the steel cups holding the rubber bushings in a plane parallel with and aft 
of the firewall. Here is another of Perry's drawings (top view) showing one 
of the four tubes connecting the two top  steel cups.

I always recommend making a 1/4 scale model from 3/16 square balsa or
welding rod. It is a great way to see if you have enough tubes to make
the mount rigid. As I recall Perry made just such a model.

Paul Lamar
 
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