Interesting point.
Took a look at the mech drawings for each as well, hard to tell since the adapter on the 900 isn't shown mounted, just floating. But since it's a 5.25-3.5 adapter, I would think it mounts directly into the case instead of to the drive/fan cages (where the interior should be 3.5", right?).
I'll call support tomorrow when they're open and ask. Friggin holidays.
I've got a bay adapter around here somewhere, I'll just use that without a bezel for now, and cut my own bezel if need be.
Thanks for checking it out.
-z