Well,
I have a two site with similar structure.
So,one ad setting color,border,background combination will work for both site.
To track thing one way to go would be
make ad for
channel1-site1_top

again make ad with same settings for
channel2-site2_top

though simple it seems repetative and i have seen that google doesnt allows having multiple channels for same code.
But i actually dont know how does it work.

Means i have tried but it seems that tracking is not accurate ,may be overlapping somewhere as sum of channels income is higher than total income.

so any one can explain how is it done.

As it seems repatative i dont want to make 2 codes and rather use 1 code for both channel and get accurate info from both