I have a 10x16 shack. The ridge beam runs across the 10 ft section of the shack. I have a 2x6 evaporator that will be running perpendicular to the ridge beam.

If I put the cupola over the ridge beam (perpendicular to the evaporator, will this be an issue?
How big of an opening should I have for the cupola with a 2x6 evaporator? Is 3x8 sufficient or oversized? And should the size change if it is perpendicular to the evaporator?