when i was washing my seat covers (back when i had the cloth) i had to completely disassemble the top portion and reach my hand under the frame to get the headrest out. you'll see once you take EVERYTHING off.
I also really struggled with mine (on the fox). It can be bad if you have a vert and it ever rained while the top was down (I was fighting some rust holding the pieces together).
You can use a screwdriver up the back (from the bottom) or use a hacksaw blade down the back of the channel from up top. I had to go from the bottom (at the time I had almost 18" forearms and ripped the seat a little).