Removed the GPS antenna bracket and painted it with white engine paint
Opened up the 3/16" engine mount holes to 3/8". I started by placing the engine mount against the firewall and holding it in place temporarily with 3/16' bolts. I determined that the holes needed to move inward and upwards/downwards toward the center of firewall. I used a method I read on another builder's blog to drilled the holes. I started with a unibit and applied pressure in the direction I wanted to move the hole as I drilled. This worked well and I was able to move the hole as needed while opening it up through the stainless steel firewall to 3/8 inch. I then switched to a conventional drill bit and drilled the rest of the way through the backup structure. I did this for all for engine mount holes.
Bolted the engine mount in place.
Made a temporary bracket for the cabin heat control cable and experimented with various places to mount it in the cockpit.