Default unit settings for new .CPT files

Never had the need to do this before but I actually decided to open a new file using File > New. It opened a small window in CPT format. In Document Properties I noted the units were in millimetres. My default, I thought, was set for Pixels. I checked Tools > Workspace > General > Distances > Units and there it is, set for Pixels. However, I noted in Ruler, Grid and Guidelines it's actually millimetres. I can't see how to change the default for New files so that they open up universally in Pixels. Any help appreciated.