It doesn't matter much, inside or out, as long as it is straight. One guy a the field builds the antenna in the wing and uses a servo connection pin and socket to make the connection. I use a piece of plastic tubing as small as I can find and build it into the fuselage with an exit rear the rudder. Depending on the size of the plane, I either have nothing showing out side the plane, or just an inch or two. I just finished a Pheonix Fun Star and I used a tube and put the antenna in it, taping it to the end of the tube. I pushed the tube int the fuselage as far back as I coud and used some thick CA to spot glue it to a a former. There was about three inches to much wire so I puulled it forward into a long loop and taped it to the bottom of the fuse. Works fine.

I don't like it hanging outside the fuse, especially up to the top of the vertical stab. I loop a cord over the tail holding the plane on the bench and It pulls on the antenna if it is run externally.

Don