If you're worried about taping the outside of the tub, you could always put a small square of tape and attach it to the longer piece of tape to keep the area exposed in the hole smooth like the non-adhesive side of the tape. Does that make sense? You know like when you stick tape together, except only stick it to the area where it's exposed....
Trying to describe what I mean isn't as easy as I thought lol.
So, I drew you a picture
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