This option works on 4 nonces per thread instead of 2 and may increase speed mainly if you do not underclock your memory, but feel free to try it out. Note that if you use this, you will more than likely have to decrease your WORKSIZE to 128 or 64.
I'm using a 6770 @ 1.01Ghz with phatk 2.2. When I run the memory clock at 300Mhz with the VECTORS option, I get 234.5Mhps. However, I can't seem to reap the benefits of VECTORS2 or VECTORS4 at a higher memory clock (i.e. 1.2Ghz). I've reduced the WORKSIZE from 256 to 128 and 64 and peak around 213Mhps; with these options, I can only achieve between 204 and 213 Mhps.