2 Layers and got extended for 1 year
I got extended where I had 2 layers between my client and my company. I got the letter from each of the party involved that is- client, main vendor, vendor. I also got an SOW which was between Main Vendor and Vendor where it didn't list any rate. I am sure you can get the same. Hope that helps. It seems that my Main Vendor's immigration attorney (one of top 4 in the US) was very confident that with an SOW, it is not difficult to get extension.
Hope that helps.