Hi.
Before the rainroof damages your tunes : cover the top of the radio.




If concerned about ventilation/cooling of the radio, the high-end model radio with the amplifier under the seat doesn't get hot. The low-end may, but will not be hotter than a summer day under the sun. And better than a dead corroded wet radio.

 

Well I know you’re way more up on electronics than me, but I would be really leery about blocking the ventilation.

 

Valid point. Sides and bottom were not covered. Today was 96F, behaved fine.

 

Also not wrong to re-coat the PCBs to protect them against (electrolytic) corrosion. Moisture can be present in such an application, that's why PCBs in automotive applications have to be sealed always, especially after some repair work. The coating can also crack over time because of extreme temperature swings and vibration. I use this spray conformal coating which is easy to apply. It's also available as fluid: https://mgchemicals.com/category/con...rmal-coatings/

 

This

 

Conformal coating is a great internal protection - too late prevention.
Done after the radio had to be dismantled from the damage from the rainroof dripping and after successfully repaired... [If not repaired, is is useless to coat]. Not before the damage happens.
Nobody removes and dismantles a good working dry radio to apply the coating to each internal board surface, component, solder joint and crevices. So conformal coating is insurance to avoid the second repair.
The radio is always powered by a permanent +12VBAT connection. So even when not turned on, water ingress does its electrolytic diarrhea to circuitry.