it is a pretty strong rule to have a 1-pager. After all, these schools will demand that you creat a 1-pager once you get there, why would you submit more than that?
If you do submit more, you'll have the potential of having your brightest points being glossed over. And don't even think about submitting more than 2 pages. There are tons of applicants and students in your shoes each year and they turn out 1-pagers. It's just like writing a 400-word essay. Sure you could write 1000 words on the topic, but at the end of the day it really doesn't add that much more.