My 3 tubes are hashing  at  196 to 210 GH/S per board for 2.45TH/S total at stock clock, with 1 stock fan.

Am I just lucky, or is it something I've done differently?

Well, I'm not sure, so here are my observations.

1. I think assembly technique is important. I applied the thermal pads to the heat sinks first, then made sure there were no air bubbles under the pads. Then I used an impact driver to tighten the screws in a random pattern so as to equalize board contact with the heat sink. I have the fan blowing "in", and faced the handles "out" as some others recommended.

2. I used high quality power supplies providing at least 250watts per blade.

3. I placed the tubes on a wire rack shelf providing airflow to all four sides.

4. I'm using Slush's pool with bfgminer 4.7 as a proxy. I know it should work fine without the proxy, but I hesitate to mess with success.