Tonight, I drilled 2 1.5" holes, then cut out the area between them as shown in the picture.
Drilled 7/8" hole on the lower side (plans said use 15/16", but I could not find a hole saw, and the only thing that fits thru there is the tailwheel mount, which fits fine at 7/8".
Cut clearance notches on all 4 corners. Deburred all cuts.
