Pitch-diving is a wonderful means of expression but increases the risk of tuning problems.

Some modern styles of Stratocaster have graphite nut (string guide) / roller nut / locking nut with fine tuners and locking machine heads etc.

On a vintage style of Stratocaster a drop of lubricant e.g. WD40 applied to the string grooves of the nut. when strings are changed, reduces friction and helps keep guitar in tune especially when using the vibrato/tremolo arm.

I use a clean nail varnish bottle and brush (to store and apply) as aerosol can is too coarse.

Graphite in the form of pencil lead is also an effective and convenient lubricant but may look unsightly on a white nut.

I use a stiff adjustment on the springs with bridge plate heel set 1.5mm above body.

Set the springs, my guitar has three, tight enough to ensure no movement of vibrato/tremolo arm when string G (3rd) is bent one tone at fret 12.

My string gauges are:

.008 .011 .014 .028 .036 .050 inches.

0.23 0.28 0.36 0.71 0.92 1.27 millimeters. 

This results in a firm action likely to ensure accurate return of mechanism.

Now I can "Dive-bomb" to my heart's content :)

More of Bob's guitar playing tips at: www.houlston.freeserve.co.uk/guitar.htm