The only issue with that plan is that you will not be able to calculate total usage without the IoTaWatt knowing what the inverter is putting out.
For example if the mains show a net -2500 Watts you are exporting 2,500 excess Watts of power, but excess of what? If the inverter is putting out 7,000 Watts, then you are using 4,500 Watts. If the inverter is putting out 9,000 Watts, then you are using 6,500 Watts. So IoTaWatt can do the math, but it needs to know the value of the variables. I would recommend that you put CTs on the inverter if you have enough inputs, and plan to upload both generation and consumption from the IoTaWatt.
If you plan to stay the course, I’s suggest you put the mains CTs downstream of the solar feed so that they measure consumption and let PVoutput determine net with the inverter data.