Ecodan energy monitoring - can I connect an external pulse meter?

I’ve been running an Ecodan ASHP for 18 months now and gradually getting to understand its performance. I’m using Home Assistant to log data on energy inputs, outputs, internal & external temperatures, wind conditions and other things and have a growing understanding of what’s going on. However I’m frustrated by inconsitencies with the Ecodan’s energy figures, which I’m getting daily through the MELCloud API. I only have basic energy monitoring (EMP1 in their parlance) and I appreciate how basic this is in estimating the energy output. However it is also poor at estimating the kWh electrical consumption as well. I have a MID certified meter on the supply to the Ecodan which rarely corresponds to what MELCloud says. I see that it has a pulse output which meets the spec of the meters in Mitsubishi’s EMP2 energy monitoring pack (only 1 meter though as we don’t use the immersion). I can see from the documentation how to connect it (TB1.3 pins 7 & 8) and I know the FTC5 is set up to accept pulse input. If I can get it working I believe this will force MELCloud to use the MID certified energy consuption.
Has anyone done this successfully? Are there any pitfalls I should be aware of?