Making a clean seam on both sides?

Hi all, another question here. One of the parts I plan on attempting down the road is an air box. There are some complex curves and I’m sure that there will need to be some snipping, etc. at one point to make it all fit properly.

Well, I was at a motorcycle show this weekend and got a good look at a carbon upper fairing on a motorcycle. Right where the two slopes meet to a point at the front of the bike, there was a perfect seam on the outside of the fairing all the way across the front. I looked at the back of the piece and it had the same perfect seam across the back. I felt it and it looked as if during the layup process they had laid some sort of clear tape down to join the two before laying them in the mold.

What sort of tape do you think they used? Are there other ways of doing this if the inside doesn’t need to look as perfect?

scotch tape works