Because I wanted to work with canvases that I could print at a known size later, I worked out what pixel sizes the canvases needed to be for A3, A4, etc.
Anyway - since I went to the trouble of working this stuff out I thought I'd share my canvas presets with the community.
Click on the Download link to the right to get them.
How to install:
For ArtRage 3 (All versions)
* Unzip the file somewhere
* Copy the files ending in .spr
* Open a file browser (WIN+E)
* Enter %APPDATA%\Ambient Design\ArtRage 3\Resources\Custom Sizes
in the location bar and press Return
* Paste the files into the folder
* When you start/restart ArtRage, the presets will be available in the options pop-out when you create a new canvas.