For you mathematicians..

[Jon Page]

There is no magic bullet. You can reduce the degree of tension change
by tapping down the loop at the hitch pin (insuring a firm seating) and
then lightly squeezing the back scale lengths together just in front 
of the hitch pin.
This removes the natural curve in the wire which will not need to 
'straighten out' further.

I also use a pair of parallel pliers to squeeze in the becket and then rotate
on the coil to coax the wire around the pin.  A loosely-grouped coil does
not necessarily mean slippage but it looks much better if the coils are
tightly grouped; so pull up on the wire while bringing the string to tension
and tap the coil down to insure that it's square on the pin. Neatness counts.

Also remove the curve in the wire at the bridge pins, front bearing bar/agraffe
and counter bearing.

This will shorten the time for the string to maintain pitch. I do 
this as standard
procedure after restringing an entire piano. It dramatically reduces 
the 'settle-in' time.
-- 

Regards,

Jon Page