here is how i got 400 with my 7870 (gigabyte 3x fan version)
core: 925
mem: 1375
voltage:0.987 (or 987 in msi afterburner)
cgminer settings:
--scrypt --thread-concurrency 16000 --intensity 19 -g 1 -w 256
This was the one! Straight away worked, without undervolting, as I'm voltage locked. However, it's unusable, but it'll work great for an overnight setup! Awesome.
You have an LTC address? I tried the one in your sig and it said no.