Show Simple Ads on Main Blog Only?

Hey Guys,

I used to use Simple Ads on a Single site blog to insert custom text on every post and it worked great. However, the site I want to do this now is the main site/blog of a Multisite network.

Unfortunately, it seems on Multisite that the only way to use this plugin is to have text/ads inserted into every post on every site in the Network.

Is there a way to allow the ads to be shown only on the posts of the main blog in a network? Thanks!