I am so glad you asked.
When I was 15 I lived in Sapulpa Oklahoma. Most of her books that were made into movies were produced in Oklahoma, and Rumble Fish was filmed there as well. Anyway my mom's cousin owned a furniture store above which was a series of apartments that had not been used since I think the 50's. My mom's cousin let the studio use the apartment for Matt Dillon's apartment. I do not know the deal. Anyway my little sister was in "love" with Matt and my mom's cousin made arrangements for my sister to met him. I took her down one night and we sat in the monitor room watching the same scene over and over. Matt had just been stabbed and was on the bed. When they got it right he came down and met my sister. Photos were taken and auto's signed and that was suppose to be the end of it. But the photo lab stole the negatives and all chaos ensued. To cut to the end, my sister and I spent the whole time they were shooting on the set and got a very 2 second far in the background scene. If you did not know it was me and her you would never notice.
So that was ages ago, early 80's. I thought I would email Susan and asked her to take a read and give me a nod if she felt she could.
No reply or word, but it was worth a shot. I still watch the movie The Outsiders, consider the Full Novel Version one of the best made. For many years I used "Poneyboy" and my cyber name, quit when others stole my spelling.