Topband: What length for twisted pair two directional beverage

[Brent Childers]

To All,
 
After reading the information about the KD9SV Two Direction Beverage Antenna System. (http://www.radiobooks.com/products/sv2bevsys.htm)  I was curious about the following statement:
 
Another benefit of using twisted pair wire or WD-1A is the lower Velocity Factor (VF) of the wire: a physically short antenna “looks” electrically much longer. Using a VF of 58% for example, a 311 foot long twisted pair antenna is electrically the same length as a 537 foot single wire (one wavelength) antenna on 160 meters.
 
So if I were to use the .58 velocity factor on a 440' single wire 80M beverage, I should expect to get the same performance from a 255' twisted pair beverage.  Am I understanding this correctly?  Or is there some downside that I'm not accounting for?
 
73 and Happy Thanksgiving
 
de ww
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