Our 36" gas cooktop will have 18" of counter space on each side, and the entire 6' section will be flanked by brick walls and an arch overhead. To keep the arch at the optimal height, our vent insert will be 4.5' above the stove.

What are your thoughts on not using a vent at all since it'll be higher than the optimal 30-36"? We've always had a recirculating hood in previous houses, and used it a few times a week.