Import XML as a specific instrument

I am scanning in a french horn part and want it to be in F not C. I have tried editing the XML file and setting the part as horn in F. I even exported a horn in F part to XML to get the settings. Nothing I do works, I still have a part in C not F.

As soon as I copy the music to a horn in F stave it transposes.

What is the correct procedure for configuring the instrument without transposing. I would have thought there would be an option to change the instrument without changing the transposition.