I have this same gap on my 2400, when the slide is out there's an opening on the slide floor that allows cold and critters access to the inside of the coach. We camp in freezing temps, the opening is below the closet, when we open the closet it feels like a freezer in there. We boondock in the desert, last winter I saw a man put a 5 foot rattlesnake in a barrel, I couldn't help but think how easily that snake could crawl into my PC. The opening allows the slide to go out without interfering with an electrical post that is mounted solid, I've seen this on cheap trailers. A man told me to cut a pool noodle to fit in the opening but I'd have to remember to take it out when I put the slide in. I asked the factory if they could eliminate that opening and they didn't think so. No one seems to be too concerned about this. Any ideas.