Hi Hairypalm,
Getting the tape right up to the edge of the base can be tricky. And if you do get it there then in time the unit can move as the adhesion on the tape breaks down. The longer you go without changing the tape, of course, the more breakdown and movement you'll get. On areas like the back and sides that aren't visible I put the tape right up to the edge of the base. But on the hairline I set the tape back about 1/8" and then glue the the edge down. This provides for an undetectable attachment. Another advantage of doing this on the hair line is that it provides a smoother transition that just putting the tape to the very front of the base.
Regards,
John