htautosjay - it will vary to be honest. With the per-hashboard feature, I've been able to get +5% out of batch2s. That isn't 16k on most, but is an additional 5% from baseline. Tuning takes some work though. Dev fees are disabled until 12/1, so you are welcome to try it on a mini and see.

To tune:

1) Set global frequency to 650. Set each other frequency to "Use Global".
2) Observe your boards for at least 10 minutes, if any drop out, on the next cycle decrease their frequency by 1 step in the pulldown.
3) Repeat this cycle until you have a stable minimum frequency for your boards.
4) To start the 'upwards tuning', choose one board (#1 for example) and increase it's frequency by 1 step.
5) Observe the board for at least 10 minutes to see if it is stable. If it is, repeat #4. If it is not, drop down 1 step and move to the next board.

Going through this process (which hopefully makes sense), you should be able to tune your units for your individual system maximums. It's best to do this with the fans set to 100% so you can remove thermals from the equation -- after which, set the fans back however you want them and see if your boards stay stable. If they do, good, of they don't, eithee decrease freqeuncy by 1 step or increase fan.

Good luck!

Jason