Many people place aluminum foil on the sticky part of the uth so they can move it from tank to tank when needed. Pulling uth off can damage the heating elements within. Be very careful when you do it.

Using foil tape to reapply will work well. I have always placed the uth probe between the cage bottom and the uth and from time to time had areas of the uth not be completely in contact with the cage bottom but it has still heated well. That will depend on your cage type.

You may need to try and see how it works with your setup. You are on the right track.