Many thanks, I still have my voltage discrepancy on the emonpi, where it suddenly started to read 10v under at 220v when the emontx reads 230v (old thread on this: Change to Voltage Measurements?) but from the start I was never seeing power output over 4500W which did not seem right as the inverter is rated to 5kW and there is 5.7kWp of panels so I should be over 4500W at peak mid-day output.
Looking on multigraph the clamp and the inverter are tracking very closely now, I will see how it goes once production drops to lower numbers and if the inverter kWh/day gets closer to OEM kWh. If I remember I will have to see what the FIT meter compares in a day to the numbers as well.