Here is a trick for the top motor mount bracket you might try Ken.
You will have to cut some of the casting tabs off the tops of the 
rotor housings and drill and blind tap them for mounting holes.
There are a couple of useable bosses on each rotor housing already

This is not 1/2 inch alloy plate but it looks like it.
As I recall it was aluminum honeycomb.

Paul Lamar
 
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