Natural Attacks are all considered secondary when combined with Manufactured Attacks, so you get 7 attacks from TWF with normal iteratives. All attacks in the above example from Full Bab:
-2, -2, -2, -2, -2, -2, -2, -2, -7, -7, -12, -12, -17
That's 8 attacks at essentially Full-ish BAB and then 5 attacks that will probably miss.