How about words from an actual professional hop farmer?
http://hwcdn.libsyn.com/p/4/9/5/4950b59151d67ded/bbr03-03-16springtimehops.mp3?c_id=11078830&expiration=1463078823&hwt=ebba5e16fde7a6fe884bc3e3ae06eb00
He recommends 3 bines for aggressive strains (cascade, centennial), 4 or more for less...