Greetings!
No problem, I am always happy to help when I can.
I’m not a fan of roof vents either. I much prefer window vans with many opening windows. With opening windows, an under $20 12vdc fan will provide better ventilation than 2x $200+ roof vents, and also avoid the leaking problems.
Direct type swamp coolers add moisture to the inside air, which can be beneficial in dry or desert areas. The indirect type, does not add moisture to the inside air. They exhaust the moist air outside, while actually dehumidifying the inside air, much like a more traditional air conditioner. The indirect type is the best choice for humid areas.
This picture might help explain how it works.
Cheers!
"Opportunities are everywhere, but only action makes it happen." ~ Van_Dweller