Well , i bought a shorty; it makes sense that the stock doesn't just twist off, so Im not surprised. I took the bag off, where is the safety feature???? Pic would be cool. I got an 06 Street glide. My first bike...super clean....only 2500 miles
Check for the allen screw. You may have to pull up on the rubber cover at the base of the antenna to expose the screw. If you try to unscrew the antenna and the allen screw is set, you will destroy the threads on the post
One of my shorty's that I put on has the allen screw, the other doesn't. The CB side did, (Ultra Classic).
Hope this helps
Ride Safe