My son applied to SLS last year the first day the window opened - December 16. He received an acceptance letter a few days later dated Dec 17. I will say, that compared to AF's SS, the applications for Army and Navy were much more "bubble" oriented. For example - Varsity sport - yes/no, community service - yes/no. After each section (academics, extracurriculars), you had (I think) 2000 characters in which you could fill in any additional information. He filled in all the space he had to add in anything that didn't fit in somewhere else. (AF's application, incidentally, was more of a "submit your resume" type).
My son's PSAT scores were not that great - 197 total (so each section in the 60 mid/high range). But he did have his ACT scores from freshman year, when he got a 31, so I'm not sure which they weighted more heavily. I think class rank and GPA would also weigh pretty equally up there with the test scores. I don't believe the sports/EC's are as important as they are for getting into the academy itself, but think you'd have to at least show some athletics and leadership.