Should have used a circle template, took your time with a dremel, cleaned it up a little, drilled seperate holes for screws, and used a fan grille... That's just a big mess you've got there...
If your case gets either bit hot, the glue from that tape will adhere to your case instead of the plastic from the tape, and when (or if) you decide to take it off, you're gonna have a gunky mess.