Originally Posted by Vengeance
God Pain is a path that can only use one tec. The actual God Path can not summon Gedo which is why it wasn't used against Naruto. Nagato on the other hand could summon it but he got caught up in Naruto's bullshit story. You also need to remember that is was assumed by Nagato that Madara & the others were busy sealing away #8 so it wouldn’t have been wise for him to summon it then.
I thought the same, but it isn't like that. Gedo Mazo obviously can't attack the Bijuu itself.
Tendou can summon Gedo Mazo. He already did, in the cave when Deidara and Sasori captured Gaara.
That means that he chooses Chibaku for obvious reasons.
And Nagato didn't know Sasuke even caught Hachibi, so he couldn't assume they were sealing the Bijuu.