Very nice. It sounds like you're testing each board and moving chips around/replacing them based on their performance and/or whether they're dead or not. Have you considered any methods to remove a dead chip from the chain without actually having to rework the board?
Well ... not exactly. This is the prototype, so it was designed to make tests and moving things around easier. The problem was that i had lots of bad chips (https://bitcointalksearch.org/topic/m.3538767 ) - from 120 purchased the first two boards didn't start at all, so had to replace some chips and the end result is 111 of those 120 working or over 8% waste.I have considered designing the new board in a way that will allow skipping a dead chip (by changing the resistor diver on SPI as stated earlier), but that makes the board huge and no longer single layer board (with only chip grounds on the bottom), so the next decision was to make shorter strings of 7 chips and be able to skip the whole link until it's fixed. It is not possible to skip a chip with a simple jumper as in the BFSB boards, because here there are different voltage levels at each chip.
As you can see from the pictures above most chips are at 54 clock, but some are at 55 - that's how they are balanced in performance, not by replacing the chips or moving them around.
... if there's chips 
