I would be very careful securing your motor in the manner you have. The nose ring in the Wind S is only light ply. A friend mounted his AXI the same way as you. It lasted a couple of months before the motor broke loose. He hadn't removed as much material as you have either....

Aircraft ply (5 or 6 ply) with carbon either side is a good solution for a firewall. Only needs to be 1/8" thick.

Regards,
Jason.