Robert Lang wrote in the 05.06.5 MMD:

    "I am moving from Mississippi to New Mexico.  Does anyone have any
    advice on preparing pianos/harpsichords for the climate change
    (humidity from 100% to 0%)?  I have an automatic harpsichord and a
    square grand piano.  Any thoughts on preparing the soundboards?"

One is tempted to suggest either a.) selling them before you go, or b.)
burning them within six months of arrival.

Seriously, I think it would be essential to install humidification in
the building, since whatever you do to the instruments, you cannot
permanently hermetically seal them.  And it will not only be the
soundboards which will be affected, but also the wrest plank, casework,
veneers, etc.

We experienced similar problems in shipping our collection from England
to Canada.  We have installed a large commercial humidifier, which is
connected to the main water supply and main electricity and is
completely automatic, with a humidistat to control the operation.  This
has dramatically improved things, and you can set the humidity to
whatever level you require.  We have it set at 55%-60% relative
humidity, which seems about right.

Good luck with the move!

David Evans
British Columbia