My Batch 1 mini came with a 3000rpm fan. I replaced it with a 5400rpm fan. set it to 100% and the clock at 750. In this config I have 1 board reaching 70deg C and the other 2 are below that. The boards are in the 55deg C range. I have a second batch 1 mini coming in a few days and I have a 6000rpm fan i will use with that one. The seller states it runs at 16kh/s as is but I feel better with the high speed fans.

Here is more data
When I am hashing at 16.9 kh/s the share rate on ZEN, @ suprnova, my share rate for the 16.9 kh/s, with 1 controler (original) configuration, is 913. In the 2 controller configuration it's 1010.
My Efficiency dropped from 99.9 to 98.8 respectively.
Round earnings went from .0367 to .0404 respectively.