Well, you're in luck! I just helped someone out with a scaled down version of a few of the elements for their smaller monitor
Once you've installed the theme, replace the folders found in C:\Users\YourName\My Documents\Rainmeter\Skins\Diablo III (or C:\Documents and Settings\YourName\My Documents\Rainmeter\Skins\Diablo III for win xp) with the folders found in this .rar
[link]I only scaled down a couple of the elements, the cpu, blue ram meter, hdd full bottom bar and launcher but I hope this helps you