How to determine Exchange rate (of type C) in invoice accounting document?

Dear all,

Kindly help in the below requirement:

To determine exchange rate type (C - Standard translation at Customs Rate) at invoice header level, so that C gets determined in accounting document.Analysis (wrt SO - 79546 and Inv - 1001180016):

Existing OB08 details:

In sales order, both at header (Sales tab -> Doc Currency) and item level (Sales A tab -> Exch rate) exchange rate (65.24 or M) is determined.
Therefore, the same gets copied to invoice header (exchange rate M) whereas exchange rate C got determined at invoice item level. This is due to exchange rate (C) is maintained in customer master.

Attaching the existing copy controls configuration.
Order to Bill (Header)

Dlv to Bill (Header)

Dlv to Bill (Item)

Test data (below is the acc doc)
SO header details

SO Item details

Invoice Header details

Invoice Item details

Since Invoice header picks M, same is shown in accounting document.

I want accounting document to determine Exchange Rate of Rate type (C) here...