Yes, my thumbnail images are huge as well.
Under your Extend HTML content selection tab of extending description and content:encoded HTML, I have both items checked because I thought I would need to extend my excerpt since I am using a thumbnail.
But it doesn’t extend my excerpt at all, it just makes my images huge. And I see that it allows the image 90% more width if you have those items checked.
What exactly does the “extending the description” and “content:encoded HTML” do to the rss feed?