Paul,
How about this mount for it's geometry? Could something like this be
modified to fit the rotary easily?
This one extols the virtue of reducing the 180 and 185 vibrations thru the
use of better isolators on seaplanes mostly. (Note the seaplane version has
two extra vertical outside legs). Costly!-The hardware alone, without the
mount is almost $2K! Add the mount for another $3.2 K or more and you are
getting up there. I like your using the McMaster Carr "isolators".

http://www.seaplaneswest.com/enginemounts.html

Marc Wiese

Classic Continental bed mount. Won't work with a rotary
directly. Needs a lot of additional and complicated bracketing.
Much much easier to use Jeff's motor plate and fully custom
mount.

BTW those Continental type mounts are poorly designed
from a pure space frame point of view. In other words they
rely on the bending strength of some of the tubes.
Consequently they have been beefed up after years
of use with some cracking AD's with gussets and tube doublers.
The C182 mount is a good example of a badly designed mount.

Here are some pictures of the one in my 182.

You will never really know what will happen so my advice is keep
and eye on it and check it for new cracks annually.

Paul Lamar