I have a daughter who is a freshman at Stevens. Although I can’t tell you if Stevens will superscore your ACT (my D concentrated on the SAT) here is a link to something called the Common Data Set for Stevens. It is a profile of their admitted students from 2013-14, so you can look at their range of ACT scores. You’ll see that the middle 50% of Math ACT scores ranged from 27-32. This means that 50% of admitted students had ACT Math scores between 27-32. Link: http://www.collegedata.com/cs/data/colleg/college_pg02_tmpl.jhtml?schoolId=71
I do remember reading a letter my daughter forwarded me in September saying that all of Steven’s standardized test scores rose yet again for freshmen admitted in fall 2015. The 27-32 middle range score for ACT math may now be higher.
I’d say concentrate on getting a 700+ on the Math2 SAT subject test. And although it won’t help you with admissions, try to get 4s or 5s on your AP exams in May. Stevens is generous with AP and IB credits and you’ll save money.