Makes a difference which way your trying to control
movement.... if you put it as a horizontal X that will
control fore and aft(racking movement) but will do
very little for vertical movement... thats when you
need a different plane to control that force... look
at a dragster... they have a bridge network on the
side rails with a angled brace in every square to control
the rail from fore and aft racking, that whole thing
controls vertical, then they have one or two X braces
to control the two sides from racking.... the magic
work in chassis building is triangulation