AutoCad 2D :: How To Make Text 2.2mm In All Of Viewports

I'm currently working on a drawing that has three different viewports with the scales of 1-250, 1-500 & 1-1000. I would like the text I've created in model space, to display at the same size (2.2mm) in all of these different viewports.

I'm using metric, and 1 unit in AutoCAD = 1m. I know that most people use 1 unit in AutoCAD = 1mm, but in my profession (working on large architectural site surveys) 1 unit in AutoCAD = 1m is the norm.

So the viewports are set at 4:1 for 1-250, 2:1 for 1-500 & 1:1 for 1-1000. I've set the text to be annotative, and to have the same scales. The annotation scale is currently set at 2:1 in model space.

Firstly, I don't really understand why and when I'd need to change the annotation scale in model space? I've adjusted it in the past to make sure that lintypes display the same in both model space and within viewports. Is it the same thing?

Secondly, by doing the above, all that I've achieved is that currently in model space the text is 1.1m high (which is what I want, and how I'd originally created it). In the viewports it is now coming out at 8.8mm for 1-250 (4 x too big), 4.4mm for 1-500 (2 x too big), and 2.2mm for 1-1000 (the correct size).

When I activate the viewports, it tells me that "annotation scale is not equal to viewport scale" in all but the 1-1000 viewport.

How can I make the text 2.2mm in all of the viewports?