Hi Martin
You beat me too it.
OCLV as per my Trek frame, when i put the vacuum on the concrete mold that i attempted i was gobsmacked @ just how compact the the laid up glass went then when it's infused its far superior to any hand lay up ( i ended up having to lay it up by hand eventually as i couldn't get the mold vacuum tight)
@DC
Sorry mate i must have misunderstood your intention, i thought you wanted a maximum ridgidity gantry using composite construction, if this was the case it would need to be one piece.
If i ever get the time i might design a 4' gantry and make a mold,as it's a good size it might be possible that other members of the forum might find this usefull.
Have a nice day guys
mekanik