It's not the most elegant method, but here goes
1. create alignments for left and right RW's
2. add LinkOffsetonSurface to each side of your assembly, make you to click
"Omit Link" - this will add a little circle to one side (endpoint of this
link). Also, delete all link codes, otherwise your top surface will be
screwy
3. add LinkVertical to this new circle (end of first link). make the
height of this link 1.2m or so, it's completely up to you. (delete link
codes here as well, but do not omit this link)
4. edit your corridor properties and go into Target mapping. assign your
RW alignments to the appropriate link subassemblies, assign your EG surface
to the same subassemblies.
Good luck
Matt K