Looking around at youtube right now for a decent video about stretching strings, I mostly found videos made by people who believe, the strings itself have to be stretched, but which is wrong you can't stretch that kind of steel permanently except just right before it breaks. You pull the slack out of the windings and of it's seat in the bridge.
OK, this guy is right on how too much windings are bad:
http://www.youtube.com/watch?v=VIwn5-3Mec8
And here's one from the same about stretching:
http://www.youtube.com/watch?v=BDPto7BcWsY
There are some videos from this guy, showing how to reduce windings on the tuning posts.
I do the stretching with more force, pulling only one string around in the middle of the string, while holding it on the first fret, so it won't be pulled out of the nut. After stretching a single string I tune and stretch, until it stays perfectly in tune. Then I proceed to the next one.
My both guitars with Dual Fulcrum Vibrato have no tuning issues, even after dive bombs.
As already mentioned, the bridge plate has to 3/16" above the deck, everywhere. So it has to be parallel and without any angle, which is just necessary for a 6-post vintage vibrato to have it floating.