My own notes on the same, from the perspective of the revision 2 A6 (I do not have any of the first model):

• Voltage- I do overvolt to 12.2V in the UI.  On batch 2 this means 12.15V PSU and provides about 3.9TH (this is a much lower voltage requirement than the batch 1 voltage).  Even during hot summer days I've had no difficulty with this overvolt.
• RPI Image- I'm running a 2016-02-05 image.  Any version is quite stable, but it can be noted that later images try to keep the temps to 68C; the original BlockC image targets 75C.  The later images that target 68C do result in some unusual fan ramping action that didn't happen with the original BlockC image, but it is easily fixed (see next point)
• Fan Speed- I've never tried the AVA4_OPTIONS for a fixed fan speed, but I do use min 40 in the Cgminer Configuration tab.  Using the default speed results in the miner getting stuck in a fan ramp up/down cycle and underperforming at only 3.2TH.  Min 40 fixes the issue.  This doesn't mean that faster is better though-- if the miner gets too cold then performance starts to drop (e.g. I tried min 70 once and was very disappointed with the 3.6TH result-- 40 seems to be the best setting for my case and provides the expected 3.9TH).  I'm still running the original A6 fans-- I have the Sanyo fans here but I haven't switched them out yet; I do not know if the Sanyo fans change this issue.