I would not tip now. Wait till spring, as the first sign of warm weather approaches, and tip at that time. I have seen to many cases where the flushes were tipped too late in the season and the buds that formed from the tipping delayed pushing or would not push at all come the warmth of "spring". It could also cause problems should we get any real serious cold spells.
Oh, and as also stated, IF you had any intentions of allowing it to try and fruit, throw that thought away if you tip it now.