As js3 stated the practice can be effective if done properly and has been standard practice for some years in RC pylon where the the drag penilty and the danger of a following aircraft of cutting off your antenna if left hanging for about fourteen inchs if done the old way.
Attend any 422 or 428 pylon event say at the nationals or any event and you will have trouble spotting any anternnas. These aircraft can and do approach speeds over 170.
I also have used the technique on many warbird racers these typically are slower but much bigger airplanes and indeed it works quite well.
For normal sport airplanes I usually don't bother but for the racers yes indeed.
Here is a little tutorial on how its done:
http://www.darrolcady.com/Racing_Inf...ch/Antenna.htm
And a few pics ot the installation in progress on a warbird racer.
John