Gordon, I’m with you on preserving shell integrity. The slight added convenience of storage accessible from the outside is not worth a large hole in the shell, covered with a plastic door that will deteriorate quickly with UV exposure, not to mention the potential for
leaks. For security you’ll probably want a keyed latch, so now there’s one more key to keep track of and one more lock in the road spray zone to get gunky and refuse to budge when you’re trying to get at your camp set-up stuff during a late arrival after dark in the rain…
I put stuff we need quickly from the outside in a bin that rides right in front of the door. Last in, first out, and the bin slides under the trailer in camp.