Glad I keep up with this thread. I found this little GOLDEN TIP!!! All of my 280xs were running at 270kh, hadnt had time to really work on it but the few changes didnt help. Dropped engine down to 1000 did it! All 12 GPUs im pointing at this coin are now humming at 350, thanks!
I use 4 x asus 280x direct CUII tops and get on average 367kh a card. If you would like to possibly increase your hash rate download this miner which is the aleks_nr3 cgminer for vert
https://www.dropbox.com/s/d771ipmoud651oo/vertcoin.rar I use this miner with no issues on any N-adaptive coin and so far it has proven to give the best hash rates for me over any other miner including vertminer and the other so called specialised miners for such coins as ultra and exe coin.
I also use this line in a bat file which may be beneficial to use with aleks cgminer which will happily run four cards nicely with temps at an average of 79c.
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer.exe --scrypt -o stratum+tcp://gpu.oakpool.com:3355 -u user -p password -I 13 -w 256 -g 2 --gpu-reorder --thread-concurrency 8192 --gpu-engine 1060 --gpu-memclock 1500 --gpu-powertune 0 --gpu-vddc 1.100 --temp-target 80 --auto-fan --failover-only -o stratum+tcp://west1.us.stratum.dedicatedpool.com:3367 -u user -p password
If this is helpful in any way to anyone please feel free to donate to so i can get some more GPU's aleks_nr3 is a bitch to get hold of now as well

Feel free to virus check the cgminer as i am not clever enough to alter it and even if i was able to i am not here to rip people off but help, unusual i know.
Donations greatly received at GcL1GCBZDdcZhkeZn8cZtP3o6Ga6ZVJwZJ