Have you considered elastomeric connectors similar to what is used to
connect LCD glass to circuit boards? An engineer at the company I work for
has used a 'Zebra' connector to interconnect 2 PCB with spacing
requiremnets similar to yours. It's basically a sandwich stack of
sillicone rubber material with layers of carbon or silver particles to
provide a conduction path. You can have very high density of connections.
The PCB connects to this elastomeric with plated PCB pads. Compression of
the elastomer is used to acheive a reliable connection.

|Geoff Parker           KK6HO           Ventura, California, USA
|geoff@rain.org