The trick with RA80's (and Fuji Eagles, and other
late 10.5"/14"
Winchesters) is to pull the HDA from the box, mount the box in
the rack, and THEN put the HDA in the box.
I believe that's suggested in the user manual for the Rx80 series.
It also has the advantage that if you have an 'accident' and drop the
casing while you're rack-mounting it, you don't drop the most delicate
part -- the HDA -- because you've removed it.
-tony