Drilling hole in ribs......stack them up, wrap some masking tape around them and use a regular drill bit? The balsa is so soft I don't want to tear it.

On the servo mounting, I have seen pictures of it done this way but the bay, or area between ribs, on this model seems wide, wondered if it needed to be divided with some framework and using the hatch on a smaller area.

Sorry guys. Newbie here.