How to make managed preferences permanent on a client Mac without Lion Server?

Question

I want the put the following plist in my Managed Preferences folder: /Library/Managed Preferences/accountname/com.google.Chrome.plist

with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
   <key>IncognitoModeAvailability</key>
   <integer>1</integer>
</dict>
</plist>

I have sudo rights to do this.

But when I log out, the folder in Managed Preferences is deleted.

Does anyone how to make this permanent?

I want to do this to disable incognito mode in Chrome.

Has anyone tried this before on a Mac?