How do you mount your engine?
Tele,
You see all kinds of things done at the flying field. Try to resist making the holes larger in the 100 though.
Your experience is a problem that many of us have faced in the past.
If the mount has a flat area underneath to hold the nuts, you could drill the holes out to clear the #8 threads and put nuts on there.
It's your mount.
enjoy,
Jim