Cupola Design

[adk1]

Does anyone have a good design for these? I have a metal roof. Is there a specific size? I am looking at a 2x4 flat pan however want to design it so that I can get a bigger evap that will evap more etc.
Also, If I center the cupola i nthe building, can I ahve the evap offset alittle? does it really matter alot? I ahve about 12' high ceilings

[Thompson's Tree Farm]

ADK1
I have 12 foot sidewalls and it works fine. You need as much opening as you have pan surface. You do not need to center your evaporator under your cupola.