Can I post a down payment with a Special G/L indicator?

I have to post a down patment.

I want to post a Down payment with posting keys 29 Special G/L debit and 39 Special G/L credit.

The system does not allow to post 29 Vendor subledger account to 50 G/L Bank account. Is it possible to configure that posting in the IMG?

A down payment Reconciliation account for the Vendor is determined to be posted by 29 and 39 posting keys in the IMG instead of the normal Reconciliation account. Is this correct?

Your help is highly appreciated.