The issue is flow more than any thing else. One way of dealing with this is to block the entire air path except an area just left and right of your engine's top 30%. Create a smooth exit pathway out via cutting free cowl flaps and articulating them to move 180 degrees with throttle setting. High throttle would require less opening.,..etc. There have been recent postings showing articulated cowl flaps with photos. Keeping it simple is the difficult part
This should really not be an issue on your SBD...
The full scale SBD has a very large airway gap between the firewall and the cowl which has a very smooth curve where the firewall meets the side of the fuselage.
The cowls on most SBD are never mounted at right angles to the thrust line to permit greater airflow.
This image shows just how much of a gap exists on the SBD. Its HUGE!
It would be really neat to see your cowl flaps open and close with throttle!