Configuring preferences and options in Outlook.com
Reverberocket,
I don't use Chrome very often ... I just Checked my copy of Chrome and I had not yet installed Webmail Ad Blocker.
So, I installed Webmail Ad Blocker into my copy of Chrome, and it worked fine ... it removed the ads (on right side) and expanded my inbox to the right (and used the space previously occupied by the ads).
You might want to try deleting Webmail Ad Blocker from Chrome, and then installing the latest version.
Also, in outlook.com, I have the reading pane turned off. If you have the reading pane on the right side of your inbox, Webmail Ad Blocker will NOT use the space occupied by the reading pane.