That picture wouldn't happen to be a new Top-Flite T-6 ARF would it?

As for threading the plastic mount, I was always skeptical but I've done it several times and it holds up surprisingly well. I think the trick is to use the correct size drill bit for the particular thread you want to cut and to make sure the hole is straight and round. I have larger 2 and 4 strokes in GP mounts with threads cut in them and so far, so good. The material on those mounts seems to work very well for the purpose; I wonder if other types of plastic might not work as well?