We installed a $" Nicro stainless steel solar chargeable vent in the middle of the main hatch cover above the salon. It changes out about 800 cu. ft. of air per hour, so keeps air circulating in the boat, looks good there, and doesn't interfere with use of the hatch. As well, in that position it doesn't catch lines and we don't trip over it. It works well for us.
Frank