I tried VECTORS4 on my 6870, since I can't underclock the memory (it's at 1050).

Results:
VECTORS
WS 64: 295 MH/s
WS 128: 299 MH/s
WS 256: 292 MH/s

VECTORS4
WS 64: 278 MH/s
WS 128: 258 MH/s
WS 256: 230 MH/s

So VECTORS4 doesn't give me any boost. But thanks for putting it in. New functionality is always a plus.