Story size - Different sizes on the slides in the same course

Quick question. I'm looking for the opposite of what the user is asking above. Instead of fixing slides of different sizes, I want to have one slide in the course with a different size. 

Use case: Storyline interaction imported into a Rise course that offers learners a chance to think through how they will construct a product pitch. Learners are asked five questions, one question per slide. They type their answers in a text entry box on each slide. I use variables (I already know how to do this) to collect their answers onto a single slide (slide 6) and give them a Print button so they can print or PDF their answers to be used later during a Capstone exercise.

I'd like slides 1-5 to be standard 16:9 layout. I'd like slide 6 to be approximately letter/A4 size. 

But I can't figure out how to change the size of one slide without changing all the other slides. Can you help?