How do I create a list of users?

I'm using M_Member_Search to list users but it's defaulting the output to a max of 50 users. The following doesn't limit the output:

$heroes = new M_Member_Search($usersearch, $userspage, $sub_id, $level_id, $active_op);
$heroes->users_per_page = 1000;

How do I set the users_per_page for the output?