On Prairie Schooner there were maybe 4 unused tabs behind the panel, I drilled a hole thru the cover and screwed in a sheet metal screw that bit into a plastic tab. I inserted a tiny rubber washer on the exterior screw head. Worked fine for 18 months until the new owner took over and is still working, I'm told. I'll have to wait until possession of the new style cover to make an assessment of adding additional security. I will note that an internal switch for the Texas fan will be a priority to eliminate the need to open the door needlessly and save wear and tear on the plastic components.
"Never in doubt,..... often wrong!"