Wasn't real happy with that arrangement, but if there is one characteristic of a HobbyDr project, it's organic. It may end up far from where it began, and I've never had a problem gutting my work to improve it. And we all know how I loves me magnets. I would make the upper story removable for access, allowing me to strengthen the opening. Two pairs of magnets at the rear, and two pairs in the (now enlarged) wings, and the upper story snaps and holds securely.
While working on the outer walls, I decided to go with the second option. Here is my progress after about six hours.