Emory:
I am building a Black Magic electric fuse and Rick at:
www.midatlanticairframes.com sells a motor box (very similar in design to the IMAC types of motor boxes and made of lite ply) and a firewall (F-1) for the electric version of the plane. The motor box glues/is inseted into F-1 so the firewall takes the torque load rather than asking the cowl to absorb the load. It is for an outrunner but it will work for an inrunner. I have attached some photos of my motor box for the VF 3 electric. you can fit the motor box to the existing firewall if you are willing to do some gringing and fitting. Try contacting Rick first and see what he can do for you. The price is very reasonable for what he provides.
Ed