[schickmaschine]

I should have been more exact.

I see several possibilities. As long as the Kyuubi Sage is produced it really doesn't matter. I also think that Naruto will have an unlitimited Sage Mode but as long as it's long it doesn't matter.

Possibility #1

  Spoiler:  

It's Sennin Mode I need to use. First I should work on extending how long I can use it for.

Possibility #2

  Spoiler:  

Here, Naruto starts gathering natural energy while moving. It's possible that Naruto will finish this ability so that he never runs out of Sage Chakra. In that case Naruto would gater the natural energy and combine it with Kyuubi's Yang chakra to make an infinitely large amount of Sage Chakra.

Possibility #3

Or you're right and Kyuubi will simply make an unlimited amount of Sage Chakra out of Yang Chakra and the Natural energy it gathers. However, Naruto will have to transform Kyuubi into a different being. In that case you're right, Kyuubi will take the job of being absolutely still and Naruto will use the sage yang chakra created from it.

  Spoiler:  

Even Fukasaku needs to remain still but the same rules account for Kyuubi. The question is whether Kyuubi can automatically gather Natural energy or whether he'll have to practice it.

All three versions allow Naruto to enter a Kyuubi Sage state so I'm pleased with any