ORIGINAL: w8ye
I have done four of the 40 size Ultra Sticks
Two of them I redrilled the bolt holes in the fire wall
The last one I used the metal motor mount as a pattern and redrilled the plastic mount
I use the Great Planes 40-70 mount
The plastic mounts are neat in that you can drill and tap the beams for the screws. You do not even have to use lock washers for the plastic will grip the 4-40 or 6-32 screws. No nuts on the back side. Just the screws into the plastic.
I consider sheet metal screws to be too soft but they will self tap and will not back out of a plastic beam.
I always drill and tap my plastic motor mounts. And I often wandered if the nuts on the back side were necessary. Now I know that they are not needed. Thank you for this information and the reply.
Todd