This firewall is designed after the original part. The cooling holes are not quite precise but it will do.

The A part is 4mm thick with all the holes of the original.
The B part is 3mm thick without holes for the motor and a smaller central hole for use of a non standard motor. Both parts flex about the same. I don't recommend it for very strong motors, but the usual ones should be OK. I didn't test the parts in flight, yet. For more strength just print it thicker.
I intend to do a version with the supports of the original plastic part in the future.

The outer 4 holes normally are used for thread screws which adjust the motor angle. For more rigidity I use them as additional mounting screws so they are larger in diameter.

Problem !!!

Unfortunately the PLA print is not strong enough. I used the 3mm b part. It broke quite fast. The print lays all lines exactly on each other which leads to a clean break line.
I use an older Cura version. Maybe better SW can use different orientations ? I don't know if another material would be better.

Renkforce 100XL

Doesn't Matter

No

0,2mm

100%