I purchased a 2nd controller board off of ebay. I have the fastest hashing board in slot one and then hashing board 2. Slot 3 is connected to the second controller i got off of ebay. Mine is a batch 1 unit. so i have 2 controller boards connected to the same pool, so the hash rate is totaled at 16kh/s combined but I have 2 workers in the pool. I get about a 10-15% increase in the number of shares processed. I had to connect a fan for the external controller to work. But like i said earlier that luck drops in this config.