fwiw, after letting the crowns grow for a couple of weeks I chop everything down to grade and start over. By that time each crown has sprouted a hundred purple shoots or more - they look like weird hair by then.
Another couple weeks later I'll pick out the best looking four shoots, train a pair up each of the two drops per crown and cut back the rest. Doing this I've not had any bulls in the mix. The plants will keep trying to send up more bines so every few days I have to chop the little buggers back.
This will be the fifth year for my 15 plants, and the yield and quality have always been stellar. I've only recently used up the 2013 crop, and I typically hit the 200g mark each year...
Cheers!