OK. With a "little" poorly documented and explained help from this forum I managed to remove my right rear window regulator from my 2003 Carrera 4 Cabriolet. I am going to provide as many pointers here as I can to make this effort much easier on the next DIY mechanic.
Thoroughly read this and other forum posts first.
Convertible top needs to be down or in the service position. Remove rear seat cushion, rear interior panel and rear window trim piece as described in this post or others. Rear seat back should be in the up position.
For removal of the regulator itself...The total of number bolts and or nuts to remove is 9 (13mm) (possibly 2 more(11mm) if your window is stuck in a down or partially up position). For total of 11.
(2) 13mm nuts - Convertible top hydraulic piston; (1) from the rear piston mount point and (1) from the front piston mount point.
(3) 13mm bolts - Seat belt pillar; (2) from the face of the pillar and (1) from the top of the pillar where the seat belt loop is mounted to the pillar. (remove the loop and seat belt pillar insert to allow regulator to eventually be removed.
(1) 13mm bolt - center of the convertible top support bracket; this is required to allow the bracket to be pried away from the pillar (see 30mm block of wood) to create clearance for the regulator to be removed. With a pry bar of some kind you should set the block in place at this step.
(3) 13mm nuts/bolts - window regulator mounting points (recommend removing these last);
(1) nut at the bottom accessed by removing a rubber plug; (2) each at the top; (1) one rear and one front. For the rear remove a styro foam plug to access with socket. For the front; if the window is in the fully up position access through the aligned opening in the convertible top support bracket.
(IMPORTANT) If the window is stuck down or partially up this front bolt/nut is not accessible. The window blocks access to it through aligned opening in the convertible top support bracket. Follow these steps...
you will need to use a goose neck closed end 13mm (6 point) wrench; loosen and remove this bolt/nut. Place or stuff a rag just under this nut/bolt to prevent it from falling to the bottom of the body cavity should you lose a handle on it.
remove rag, regulator should now be free to move upward but not out all of the way out BECAUSE the window (still attached to the regulator) CANNOT clear the seat belt pillar.
move the window and regulator upward sufficiently enough so the window mounting nuts (the (2) additional 11mm noted above in item 1) are accessible with the 11mm socket; loosen to free the window from its regulator seat. (be careful not to scratch or break the window by applying to much force)
Carefully remove the window from the regulator and you will now have sufficient clearance to remove the regulator from the car.
Remove the regulator by pulling it up first (free the bottom mounting bolt from its bracket) and then towards the rear (got to get the motor to clear the body) then straight up. Take it slow. It will come out.
Good luck. Its not really that difficult once you see what needs to be free.... and the window itself is out of the way.