Inside or outside work equally well.

A couple of caveats if running it inside:

1. Do not run the antenna in a carbon fiber tube OR close to carbon fiber push rods.

2. If you have a metalic finish on the plane (Chrome Monokote or a metalic paint) DEFINITELY do a range check before flying. I have found Chrome MonoKote and SOME metalic colored paints to severly reduce range.

3. DO NOT CUT THE ANTENNA. If the antenna is too long you have two options - run it outside the plane or replace the antenna with something like the "Hayes Loaded Antenna" (about 18" long) or one of the other commercially available products out there.

FWIW - When I run the antenna on the outside of the plane I usually come out the bottom of the fuselage and run the antenna along the bottom of the fuselage, securing to a bracket coming off the tailwheel. Look at a Sig Rascal 40 sometime and you will see the type of bracket I am refering to.