I cut mine down by a little more than half, and I haven't lost any reception at all. Re-using the origional ball will be both a pain and a waste of time. I think they sell some kind of ball type thing at auto parts stores but on mine I just used a piece of shrink tube. Just slid it over the top trimmed, then took the lighter to it until it had shrunk around the antenn...
"... but it's ok, we're going to QuakeCon!"
2007 Black LS Coupe.
Debadged, Painted front bow-tie(gloss black), Yourcobalt.com Sticker applied.
Stock head unit and speakers, 2 Rockford Fosgate P210S4's sealed enclosure powered by Rockford Fosgate P2002
Injen CAI Pow Coat Black. Front tires P195R15 Fuzions, rear still sport the stock conts.