Just borrowed a friend's box, and was taking it apart to look at the condition of the reeds. While open, I saw that the internal pickup was mounted too far to one side, and it was wearing on the inside of the bellows, cutting a 1/4" wide groove. Not holes yet, but, could get there. I moved the pickup closer to the middle, but am wondering how to do a spot repair to the worn areas so it doesn't blow at some point.
I considered electricians tape. I don't have any bellows tape. And this will be on the inside, so it doesn't have to be decorative.
I'll try the shipping tape first. I'm glad I took the box apart to check it out. I told the owner I fixed two things on the box while I was looking at it.
She wondered if she could just rotate all of her boxes through me, so I can gradually get them all in good repair.
Inside my GGFs 1880 2 1/2 row D/G is a section of a playing card .. cut to a strip about 1" wide and creased then glued over the worn/torn fold... very cool.
Gaffers tape might be a good choice. It is quite strong, like duct tape, but it doesn't leave a gunky mess like duct tape does if you try to remove it.
I have used gaffers tape for internal attaching and sealing of different things.