What's your proc? i tend to set affinty to core 3 and 4 on my dual gpu setup, gives me a little bit of breathing room on the front cores. However, if netflix is using the most recent version of flash, flash does do gpu hardware acceleration, thus stealing your hashes like a dirty troll.

Bringing down that mem clock can give a little headroom, maybe and extra 10 MHz out of the core, but well worth it.

I'm using -v -w 128 -f 1, sometimes -v -w 192 -f 1, haven't seen much difference. I'm getting 435-450 avg, but that's also with Ati Stream SDK 2.1 (huge upgrade) and an oc of 1040 Core, 300 Mem, and 1.22 V.