Changing default mesh size Sorry for asking, but I couldn't find my problem elsewhere.
I'd like to have the default dimension of newly created objects 20x20 instead of 2x2 units. The reason is, every time I create a new object, I have manually scale them up to my mostly needed size, which is 20mm.
Regardless of whether unit scale I select (mm or cm), the default cube is either 2mm or 0.2 cm, but I'd like to have a 20mm default cube.
Where can I change this?
This won't be an instantly workable answer, because this is an issue that I'm having trouble with, too.

But, it seems like you could maybe unregister the operators, then reregister them with your modifications. Checking out the Python API, I found: https://docs.blender.org/api/current/bpy.ops.mesh.html  

eg: 

unregister()

    bpy.ops.mesh.primitive_cube_add(size=2.0, calc_uvs=True, enter_editmode=False, align='WORLD', location=(0.0, 0.0, 0.0), rotation=(0.0, 0.0, 0.0))

register()

    bpy.ops.mesh.primitive_cube_add(size=20.0, calc_uvs=True, enter_editmode=False, align='WORLD', location=(0.0, 0.0, 0.0), rotation=(0.0, 0.0, 0.0))


or something like that in an __init__ file?

I hope you get an answer, as I'd like to do the same for meshes, but also clip distance for cameras!