Engine mount clearance

Good morning everyone,
I am hoping to have my engine mount (tail draggin 7) attached to my firewall within the next few days and was wondering. I have seen build websites in which part of the firewall was cut out/grinded down to allow clearance for the landing gear, but I can?t seem to find any measurements. Does anyone know where these are, and if they aren?t published, what would be an acceptable clearance...1/8, 1/4??
Thanks in advance,
Brandon

The mount, just, goes on to the firewall without modifying the lower part.
Then if you put a flashlight/led light on top of the leg socket on the mount, the resultant illuminated area on the firewall below the socket is the part that needs cut away for the legs.

You can mark it, with a little difficulty, or simply grind the illuminated area. Others used a carbide burr for the job.

Cheers
Ian

Just remember, that whole area gets covered with a fairing.