No, I didn't use synthetic fluid. Just Dot 4, fresh from an unopened container. I've read quite a few stories about synthetic fluid and since I never track the car I decided just t go with plain, as it were.
The 20 degres refers to the angle the raised flange/lip on the piston meets the oncoming rotor, measured in reference to the frame. I think it's designed so the piston puts the pad down evenly, without the pad chattering against the rotor. I don't know if this is an issue with the S cars but I know the NA cars need this done - the single-pot calipers.
Here's a link with a good pic:
http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/128110-piston-orientation-during-brake-caliper-rebuild.html
Hershey... That'd be nice!