For 40 and 60 size I usually just put a pin in the vertical fin and loop a rubber band around the antenna and hook it to the pin. I was always told to be careful about metal to metal that could generate RF interference. For 19 size planes I route the antenna to to the vertical fin then 90° down to the outside of the horizontal stab. I have been told this is actually good since the antenna is never straight on the transmitter.