Modbus: Send custom frame?

I have a Growatt Inverter with SDM630 that is connected via USB - RS485 Adapter to HA.
Requesting different values from the inverter work fine…
Now I found in another forum a topic with the information that it is possible to request data from the sdm via the custom function-code 0x20.
Is it possible to send a request like this 01 20 00 4C 00 02 xx yy (x/y = CRC)?