Soffit and ridge vents are pretty restrictive and will have a hard time handling large amounts of air. Adding a gravity gable damper might be a good option...just make sure you have the damper capacity matches the fan size.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD