I think one of the best deterent (sp?) is dark tinted windows.  I have
an 87 GTI that has lost 5 stereos over the years.  My van (which has the
tinting) has had no break-ins.  There is often a van full of goodies too
but it is darn hard to see inside with out being really obvious that you
are looking in.

Haven't been following this thread so if it has been mentioned already I
apologize...

Chet
-- 
Chet Douglas - CRD Consulting - Peripheral FW,SW,and Drivers
(541) 754 - 1817