BlueNRG2 - Packet Length extension (Tx direction)

[MBRAI.9]

using BlueNRG2, I'm trying to send long packets (> 20 bytes), I added a custom service with characteristic supporting notification and indication with a size = 40 bytes. After the connection established, I send a LL_LENGTH negotiation to update the TxOctets to 40. the negotiation was done successfully but when I send a long packet, only 20 bytes were sent.

I tested 2 ways, using (1) hci_le_write_suggested_default_data_length and (2) hci_le_set_data_length

Is there any way to "unlock" the long packet sending ?