Different display options for different RSS feeds

Hi,

I need to set up a separate RSS feed for a sister site, and I was able to get it up and running using the Feed Wrangler plugin, but what I want to do is customize the second feed so when it goes to a widget on the sister site, it displays a summary version of the posts going there, while at the same time keeping the full post in my main feed.

I have a php file for the secondary feed, but I know absolutely nothing about php, and couldn’t find anything to point me in the right direction as far as doing this kind of customization. Anyone have any thoughts on how to set this up?