Magstad users

Never been a concern of mine.
Everything in there can have water drip on it without any issues.

Ten years with MadStad and never has been a problem.

Yup, same here, madstad’n for 2 years and no issues or concerns whatsoever, it’s a fantastic system. It, a quality mount for ur phone ( we use a phone for music & navigation) a tpms ( ours has its own monitor) is the three most useful, practical & cost effective upgrades you can have, for sure is our most used on the everyday

I used this stuff off of Amazon.

Rubber Seal Self Adhesive Weather Stripping, Car Rubber Sealing Strip B-Type Alternative for OEM Universally Fit for Full 4 Doors https://a.co/d/1AiC6H4

Radio is sealed no worries there and even adding an aftermarket amp it is very unlikely to see any water. It's overkill to seal up that gap but go for it if you feel better.