Question about colorspace and order

[aabxx]

(file is yuy2)
<lots of filters>
LumaFilter(-2)
Unfilter(3,3)
Converttoyv12

In my script, I convert to yv12 in the very last line, because that's xvid's colorspace. However,

1) Would it be wiser to convert to yv12 before the chain of filters? (they support both yv12 and yuy2)
2) Is it better to have Lumafilter/Unfilter before or after yv12-conversion?

[foxyshadis]

Doesn't matter, really. You have a minor speed penalty using yuy2, and more choice in filters using yv12, but it won't affect quality. The difference is around 10% avisynth time, a lot less when you're also encoding.