I believe all of the bijuu chakra is required for Rikudou Sage Mode. The Juubi was nature itself, upon being seperated into nine different chakra massess, they are still one with nature.
Hagoromo yang chakra was naturally mixed with the juubi's as its first jinchuriki. Now when Ahsura was born, he naturally inherited the sages yang chakra. This granted him the Body and allowed him to utilize the bijuu's chakra even though he wasn't their jinchuriki, similar to Naruto. When hagoromo bestowed his yang power(which includes juubi chakra) upon his son and naruto, they unlocked RSM.
Hagoromo clearly still has juubi chakra, as his form still resembles when he was juubi jin. Now notice, only juubi jins unlock RSM, like madara,obito,etc. No one else ever obtained this mode, not even hashirama due to lack of bijuu chakra.
Rikudou Sage Mode is when one harness the nature energy of the juubi/bijuu, thats why upon entering RSM Naruto was able to utilize all the bijuu power/kkg.
This also explains Ashura's avatar with gudodama. :Sparks:
Hagoromo yang chakra was naturally mixed with the juubi's as its first jinchuriki. Now when Ahsura was born, he naturally inherited the sages yang chakra. This granted him the Body and allowed him to utilize the bijuu's chakra even though he wasn't their jinchuriki, similar to Naruto. When hagoromo bestowed his yang power(which includes juubi chakra) upon his son and naruto, they unlocked RSM.
Hagoromo clearly still has juubi chakra, as his form still resembles when he was juubi jin. Now notice, only juubi jins unlock RSM, like madara,obito,etc. No one else ever obtained this mode, not even hashirama due to lack of bijuu chakra.
Rikudou Sage Mode is when one harness the nature energy of the juubi/bijuu, thats why upon entering RSM Naruto was able to utilize all the bijuu power/kkg.
This also explains Ashura's avatar with gudodama. :Sparks: