There's a set of rules on what makes a course eligible for records. Boston doesn't cut it. You can try to get the IAAF to change the rules, but good luck to you. Paula Radcliffe has the world best for the half but not the world record because the Great North Run is a net downhill, despite not being the fastest of courses (sound familiar?). The rules are in there exactly so you can't have net downhill courses or courses where you're likely to have a wind at your back the whole way, like they did today.