FreeBird, basicly the plywood plate allowed me to utilize the exsisting engine mount holes and blind nuts, it also gave the distance from firewall to back of spinner clearance. The problem with using the 170 mount spacing is in the support arrangement for firewall and accessability to properly attach blind nuts. I also placed the throttle servo below eng. on firewall, this not only made linkage simple, it also helped with balance.
Speaking of which, balance that is, by placing 1400 4.8 sub-c ignition pack by the fuel trank and 7.2 AA nimh behind tank, the plane balanced perfectly with no additional weight.

RCTEN