How critical is the drain close to the lowest point of your diff? Meaning, do you wheel a LOT or just occasionally?
One fix--If you wheel a lot, mount it off to the side some and for as often as you change the rear diff fluid, jack the opposite side up so the drain is now close to being at the lowest point...
Another option- remove the lowest stud on the 9". Replace it with a nut that is welded in place. Now you use a bolt for that spot and you just put silicone on the bolt and you will not have a leak. I've done this 2nd mod on several 9" rears and it works great...drains slow, but who cares. Drive it before you drain it so it's hot and drains better.
How often do we change the rear diff fluid anyway... these make it easier...