Different page size for singe slide

I want the results slide to be larger than the other slides. When adjusting the design menu's size attribution (*) all slides are adjusted although only one slide is highlighted. 

Reason is: The results slide is printable as a PDF, but in it's current format it only uses half of the available space on a Din-A-4 page. I want to have the results a bit more spread over the whole portrait size. 

Thanks in advance for your help, fellows.

(*) as described here: https://community.articulate.com/series/articulate-storyline-360/articles/storyline-360-setting-your-slide-size