Doug ... I haven't any experience with this type of stick, but looking closely at one of your pictures, it would almost appear as though the perch is actually a "cap" affair, and it has knurling around the lower circumference. The presence of knurling usually indicates that something has been designed to screw on and screw off. Knurling provides assistance in getting a grip on whatever needs to be taken apart. There is also a recess locating just under the perch cap, which is also a good indicator of something that's been threaded into place. I'd be willing to bet the perch cap threads onto that collar at the top of the stem. It's worth a shot. I've "doctored" one of your pictures to help explain my "theory".
Jeff Lamb