I second that: Get a fan and cool the Ant miner down.
Look in here:
https://bitcointalk.org/index.php?topic=7216.0 for plenty of examples using BE's and other miners.
Also look earlier in this topic.
You don't need any special heatsink under the 2.2gh/s.
The only thing that might be an issue is the noise from a fan due to the location of the setup, if I can get the same level of cooling from a heat sink I think I'd rather do it silently.
I think some of the issue may be due to the fact that it's plugged into the USB port directly and is chip side up, so the heat sink is below, perhaps this is meaning it's dissipating the heat less effectively. I've ordered a 1m USB 2.0 extension cable to allow me to reposition the thing.
Here's the result after an hour of 0581 mining:
https://dl.dropboxusercontent.com/u/48985321/cgminer2.jpgAs expected hash rate but worse HW, up to 5.36% now.
