After you've made the rear brakes work correctly, they still won't stop you as fast as the front brake. The front brake alone will stop you 3 times as fast as the rear brake. Fear of flying over the handlebar is overblown. When you apply the front brake, brace your arms against the bar and slide your butt back on the seat. Try it. For more info, see the web pages from the late, great Sheldon Brown: http://sheldonbrown.com/brakturn.html
HTH