I have a 4*40 and I’m mounting a Saito 72 on it. I have to turn the carb around for my pushrod to control the throttle. Now my needle valve will hit.
So first of all, what is the best method to cut the plywood? And second, what is the best look? Trim the whole side down or just cut out a circle.
Any pictures would help.

A Dremel with a sanding drum works nice. My pref. is to make a hole.

If you have to cut fiberglass a "side cut" zip bit or it may be known as a drywall cutting bit is awesome.