Some things to try...
Attack the back...
* Reach back and unclip the back cloth from inside (held in by long plastic strip that attaches to 2 plastic clips in the rear, pull down to unclip, see about 15 seconds into
https://www.youtube.com/watch?v=hCpiWmqC_6k)
* With the cloth out of the way, you might be able to reach the 6 small nuts (3 each side) that hold the clamshell down, then just lift it out up and of the way giving you full access (first pic here :
http://986forum.com/forums/diy-project-guides/66002-remove-clam-shell-better-engine-access.html)
* Alternatively (or after the step above) unclip the drive cables and run them with a drill to open the top manually (fig 6&7 here
https://www.pelicanparts.com/techarticles/Boxster_Tech/71-BODY-Convertible_Top_Repair/71-BODY-Convertible_Top_Repair.htm) ... be careful to only do each side a bit at a time, then swap over, do other side to same level, so as to not get either side too out of alignment.
Attack the sides
* Instead of the main 19" bolt, remove the 2 parts attached to it... (see 2nd photo
http://986forum.com/forums/diy-project-guides/66002-remove-clam-shell-better-engine-access.html)
* Front pushrods - torx screw I think, can't remember exactly, will free up the the top
* Rear pushrods - pop off with a screwdriver, will free up the clamshell
* With both removed on both sides, should be able to manually raise the clamshell and move the top