Help with RSS Feed

Hello,

I want to use my RSS feed to generate a weekly newsletter that contains the following for each post:

1. Post Title
2. Featured Image
3. Excerpt

In order to accomplish #3 above, in the Reading Settings in WordPress, I have "For each post in a feed, include" set to the "Summary" option. Then I used this filter to force GP to use the manual excerpt vs. the automatically generated excerpt based on the first 'x' amount of words.

It's exactly how I want it, except for the featured image which is missing. I can only get images to show up in the feed when I change "For each post in a feed, include" from "Summary" to "Full text" but then it literally shows the entire post. So, I need to leave that set to summary.

How can I add only the featured image to my current feed?

Best regards,
Jesse