Yes, correct...use the lug wrench (or equivalent) to loosen the two bolts. I think I read somewhere that there is a recommended number of turns to make sure the cable assemblies are fully disengaged, but I may be mistaken about that. IIRC, I backed mine out 3 turns on each side.
The problem when going back would be the inverse of not loosening enough, ie, not getting one side tight and having the motors be pulling at uneven tension from one side to the other. Biggest challenge with the motorized top is broken bows and/or motors not being in sync with each other, which usually causes the broken bow! Never had it happen, but after reading about it, I decided to go manual as well and love it that way...very similar to my Miata. When I first got my 968, I thought "how cool, a power top" but I found it too slow and a pain trying to guide it down so everything would fold up nicely. In manual mode, you can guide it as it goes down and I think it's actually faster.
- Darryl
