Machine geometry

Per the recent request for lurkers to de-lurk:

I recently received some linear components from Bill Scalione, and now
have to decide what kind of machine to build with them. I have two sets
of 1" dia. rails, 54" and 66" long. Also two tables, nominally 22"
square with two open bearings at each corner along one edge, and one
open bearing centered along the opposite edge. These tables weigh about
30 lbs apiece.

My question is what geometry will be best for a (mostly) wood router? I
like the greater working envelope that a moving-Y gantry system would
provide, but this requires a longer leadscrew and probably heavier
motor. The moving-X table system, while easier to build, and probably
more accurate, provides only half the travel.

Any suggestions appreciated.

Geoff Roehm
http://personalweb.edge.net/~groehm/