This is a very good question. First on the CRC error -- that is going to happen some and is only a problem if it is constant. It happens on even the stock firmwares depending on machines, temps, frequencies, and phase of the moon.

Temperatures will play into how far you can push these, but there is not a clear formula for that. What's really interesting is I have a customer with a large install (1000+ machines) who has observed that there is a point where the machines get too cold and slow down! I'm unsure of the exact details on the temperatures, just the observation that was shared with me.

So yes, temperature has a play both when going up and when going down.

The summers here are very hot -- my miners I had to constantly tune even through the day to get maximum out of them; they always ran best at night.

I hope this helps some.

Jason