The screws are not visible. I first drilled tiny holes for the screws then I used a large diameter bit to make nests for the screw heads. After I screwed them in, their heads sunk into their nests (under the actual surface of the wood).
EDIT:
guitman32, I made some corrections to the diagram above. Now you can see how I made the screws sink in the wood.
After I finished the glueing and the screws stuff, I used automotive putty and covered everyithing, then sanded the whole thing to perfection. Then the paint - whole neck and headstock is jet black. Now the headstock looks so damn smooth and cool. It looks really evil, I freakin' love it.
It is about to be polished soon.
I don't understand your second question but if it is about the way the surfaces of the wings and of the original headstock match, then the answer is: NO, they were not precisely square and flat - I couldn't make them even close to flat.
I didn't even put much effort to match them perfectly because I knew that the screws would clamp them extremely tight and the glue between the surfaces would fill any persistent tiny hole. And I turned out to be so right
Still, I don't mind knowing how do people make the surfaces that are about to be glued perfectly flat.