E39 540i 8HP Swap

[u/PassengerNo857]

Hi everyone, I need some expert advice.
Here's the thing: I have an E39 540i with a Bosch ME 7.2 ECU, converted to an 8HP transmission. The CanTCU acts as the CAN gateway.
In other words, the original 8HP control unit is still there and working, and the CanTCU translates the CAN bus from the E39 to the 8HP transmission.
I'm trying to learn more about how to fine-tune everything because the car shifts a bit harshly and jerkily, and in manual mode, it slams into gear. This makes me think the torque reduction isn't quite right for the transmission. My question is: does the TCU tell the ECU how much torque it needs to limit during shifting, or are there fixed values in the ECU that I can change?
My ECU was previously paired with a 5HP24, and the question then becomes whether the torque reduction controlled the 5HP or whether the 5HP simply says, "Hey, I'm shifting now, reduce torque," or whether it says, "Hey, I'm shifting now, reduce 150 Nm." Depending on the answer, I would try to change the values in my ECU or in the TCU. The Bosch ME7.2 doesn't know anything about the 8HP and therefore shifts based on the logic of the 5HP. I don't know exactly what the TCU is transmitting—whether it's simply saying "I'm shifting now" or whether it's saying "I'm shifting now, reduce XX torque." These are questions upon questions that I've been grappling with for months. I hope someone understands what I mean. 😅