Irl your best ‘chancing’ will come from your GC: s/he will know how students from your school fare at Dartmouth & similar schools. It’s one of the benefits of an ‘elite’ private school.
Sharing @ucbalumnus’s very helpful post: http://talk.qa.collegeconfidential.com/what-my-chances/2095312-generic-chance-answer-for-super-selective-colleges.html