I have had good experience by installing my antennae as follows.

Glue an appropriate length of outer case of push rod (the blue or red stuff that encases the inner yellow fluted rod) the length of the fuselage inside. Then insert your antennas through and into the blue or red casing, using the push rod casing as a holder.
I have used this method on my last four planes which include a CG Chipmunk, CG Sukoi and a Top Flite Corsair.
PaulR