Which ranks of concubine resided in the gong and yuan respectively?

Question

Background/ TLDR

Having at long last gained access to this source by a certain Mr. Woo and with the support of the answers to my previous question I can finally gather some statistics on successions in the different dynasties. But there are still some things left unclear.

The rule of succession expounded on page 629 (in my opinion he actually states two different rules, so the second, that he seems to focus on), says (to my understanding) the following:

• If there are 嫡子 (sons of the Empress) pick the eldest
• Else pick the eldest from among the sons of the 36 consorts (Woo uses “wives”) residing in the palaces gong（宫）。
• Failing even that, pick a son of the remaining 72 consorts (Woo: “concubines”) from the subpalaces yuan (院）

Note that Woo believes this rule to have remained in function between the end of Zhou and the beginning of Qing with a small change (number of empresses) in the Yuan and Ming dynasties.

Difficulty

Even if the record of consorts’ promotions and demotions in the dynastic histories is not gapless, the information therein concerns promotions to particular ranks. Never have I seen consorts assigned to 宮 or 院。As a result, I must find the correspondence between ranks in the body of consorts and 宮 or 院。

I first hoped it might be enough to identify the 36 most high ranking court ladies below the empress. This can be done for example here. But the results are very doubtful.

Instead of 36+72 =108 ladies below rank of empress, the early Tang have 40 + 81 = 121 ladies (I have now confirmed this arrangement from 新唐書 here ) .If I take the first 36, the cut would fall within 5th rank. Later Tang has but 82 in total. On the Ming the information on the site is incomplete.

Another piece ostensibly from the Zhou Rites (周禮) (but actually, I think from a commentary thereof) that mentions 宮, but not 院 is cited here. It appears though, that ALL 121 consort are classified into 宮, the higher their rank, the fewer per 宮：

六宫即前一宫，后五宫。后五宫指后一宫；三夫人一宫；九嫔一宫；二十七世妇一宫；八十一御妻一宫。后正位宫闱，体同天王；夫人坐论妇礼；九嫔掌教四德；世妇主知丧祭宾客；女御序王燕寝。

Question

Can anyone provide clear information about which ranks of consort resided in the 宮 and 院 respectively?

In case Woo‘s Information is contradicted, additional pointers as to the role of these in succession would be appreciated, but can also be posted under the more specialised question.