ok...after 18 hours of testing, well short of the 48 hours I hoped for, here is my 190 bit stream findings;

System - Win 7 64bit, cgminer 2.6.1 + phatk, cm1 #62-0432 & #63-0433
Average hash rate per cm1 = ~725MHs at pool & via cgminer Note: neither board is reaching the bounty threshold of 750MHs
Average U = 17.5~17.8/m
HW & R are very low. HW = 0 & R <5
Maximum run time between failures (resulting in need for system reset to recover e.g BSD or non-responsive) - 14 hours
Minimum run time between failures (resulting in need for system reset to recover e.g BSD or non-responsive) - 0.5 hours
Average restarts of cgminer before both boards detect successfully - 3
Identified conflicts - use of 2nd 6770 GPU for mining causes system to BSD on start up of cgiminer or intedpendent start of of phoenix miner when cgminer is FPGA only. Note: Can mine on 1st 6770 GPU though.

I hope this helps developers...
Tweakers, any idea on how to tweak to get up to 750MHs and improve stability?