Hi,
I have not try this, but it might work
1- Set the driver to print on A4 as default
2- Make sure the paper selection on the printer (Paper Size and Paper type) are set correctly.
3- Set tray 2 as your default tray
By default, the printer will ask you to load paper on tray 1 when the job you are trying to print does not match: 1-the paper Type, 2- The paper size of the default selections.
I hope this helps.
Best regards
Mike G