Hi,
Unfortunately, there’s no way within the UI to select multiple featured post. You may have to write PHP snippets for it to work and they’re not guaranteed to work.
But consider doing this:
Place 2 WPSP list within your page.
On the 1st list serves the purpose of displaying 1 column list of your featured image.
On the 2nd list, you can add an offset depending on the number of posts displayed on the 1st list so there’s no duplicate post within the page.