I would suggest that the docks be standard stereo-unit wide, even if that means having unused space. The problem with it not being that wide is that it then must be the top unit in a stack, which can limit placement.

My problem with a small docking station would be something completely different from that: weight. When building mine, I deliberately made them larger, and out of denser wood, so that they would be heavy and "stay put". That way, I could push/pull the player in and out of the sled with one hand and not have to hold the docking station in place with the other hand. Even as it stands right now, I wish I could weigh down my docking stations even more somehow, they still move a little bit. If your docking station is screwed into a rack somehow, it's a moot point, but if it's just sitting on a shelf or a desk then it becomes an issue.

With that said, though, Mark, I think your design is really excellent. I particularly like the clever use of the air channels.