[911Rob]

Forget the thermostat controlled venting.

Do you have continuous soffit venting?
If you have the soffit venting, pop some screened vents from Home Depot into the gable ends at the highest point possible. Simple, easy and will help the air flow for sure.

edit: sorry, I realize our man Vin has this covered already; so good luck.
and yes, you must have the soffits free of insulation. You can buy a foam insulation stop to insert between the trusses.