I wouldn't climb in, there is no need to. You have much better access with the fuselage rolled 90 degrees, you can reach anything. I've rolled mine 180 degrees so I can reach way back in the tailcone to work. I easily installed my magnetometer mount, seat belt cables, and static port tubing without getting in the fuselage. You can easily buck the rivets for the top skins with the fuselage rotated.
If you are building a rotisserie, you have to remember to build it high enough so the steps clear the floor when rotating. I also made sure the fuselage was level, and that the front and back have the same pivot point above the floor.