Sebastian:

You are best not to leave the antenna inside the fuselage. In order to get the range you need, it must be fully extended and, preferably outside the fuselage. Unless you have a four foot fuselage, it won't do well inside.

What I have done is drill a small hole just aft of somewhere along the top of the fuselage behind the canope, for instance, and use about a two inch piece of very thin fuel tubing, and pass the antenna through the hole, then through the tubing, force the tubing inside the hole you drilled (the tubing acts like a conduit) then hit the tubing with a bit of CA to hold it in place. Run the antenna up to the top of the vertical stab, put a "T" pin in the vert stab, use a piece of a servo arm ( you may have had to cut one or more of the unused arms off of the servo arms. Thread the antenna wire through at least two holes in the old servo arm. Use a rubber band to attach the servo arm to the "T" pin that will act as a shock absorber for the wire. Let the remaining part of the antenna dangle behind the aircraft.

That should do it. I drew a rather poor sketch to demonstrate what I am trying to get across. Hope it helps.

DS.