It can be frustrating to have Stratocaster with a floating bridge, if it does not stay in tune. I am paranoid about being in tune, and I am very meticulous about getting my floating strat bridges to stay in tune.
How do you set up the strat bridge to float and still stay in tune when you use the whammy bar? This video will show you how. Luthier Galeazzo Frudua illustrates a quick and effective way of how to set up a 2 two point tremolo bridge of a stratocaster for best floating performance.
This same method works for a vintage 6 screw bridge as well. If you have such a bridge, you have to loosen the 4 middle screws a bit, while keeping the 1st and 6th screw tight.
This will in fact make the vintage bridge work similar to the 2 point bridge, because those 2 outer screws will work as pivot.