I had a conversation last night with the guy who used to be the head of the test department for the D8B. I asked him about the problem of Version 3 software spitting out 16bit from the Mic/Line inputs.
His response was: Hmmm...yes, there was a problem with Version 3 doing that. One of Mackie's dirty little secrets was how he put it. He couldn't remember if there was, indeed, a workaround by offsetting the digital trim off of unity by some small amount (as Dan Worley mentioned). But he said that one of the major bug fixes in Version 5 addressed that exact issue.
So it would appear that Alfspanner's observations with Version 3 are actually correct. What kills me is that I had no idea this bug existed in Version 3. Not a clue. And I'm still curious why this didn't raise a stink during the 16bit Aux discovery.
Back in the days when I had Version 3, everything I recorded and outputted lived in 44.1/16 bit world....so I never came across the bug.
All the dickering I did was with Version 5....which would explain the disparity between the results I was getting and what Alf was getting with Version 3.
Which brings me to this: after talking with this gentleman for a few minutes, he said: "Why is this guy struggling with Version 3? Why doesn't he just install Version 5 and be done with it?"
I may have more detailed information on this later.