On 2/6/19 2:29 PM, Brent Hilpert via cctalk wrote:
  (I take it you mean "now look at the -left-
side".) 
Well, you know, my *other* right... :)
  However, looking at my 7970A, it appears you could
separate the cast-Al transport frame from the chassis box
 by unscrewing the 4 exterior left-side hinge screws, as well as detaching all the cabling
between them involving
 a wire harness and a dozen-or-so plugs. 
Swing the drive assembly out from the back cover--you'll note that the
pivot points on the two hinges are about 1" away from the cover flange.
 You've got plenty of room to drill your mounting holes from the *rear*
of that flange.  You might even have enough clearance for a
countersink--but that may not be necessary--the frame casting only
extends in from the left about a half-inch--you may even clear some
oval-headed screws or get away with some truss-head screws.
Alternatively, could mill a slight relief in the casting to clear the heads.
I think it's doable without removing the drive from the cover.
  For loading concerns raised by Jay, in both cases
(designed-for steel
 bracket vs drilled flange) the weight of the drive ends up being
 borne by 4 rack-screws on the left and 3 on the right. The difference
 would be steel vs Al bearing down on the 4 screws on the left, and
 some altered bending moments on the left side of the Al chassis box
 around the flange, offhand I wouldn't think it would matter. 
I tend to agree--the force is mostly downward on the front of the drive.
 I suppose that you could reinforce the aluminum housing with some steel
bar backing up the mounting flanges, but that seems like overkill to me.
--Chuck