So long as you cut the antenna length in halves or quarters, you'll be okay.  The only real reason for a long antenna is so that terrain relief has less tendency to mask your transmitter's signal.  I've cut mine on my Bulldog and put in a scale antenna on my PzIII and both work fine.  Your range might decrease a little, but I can still control them out to 20-30 feet.  After that I can't see it well enough to be trying to control it further out anyways.