Help Setting the default messaging app

I know how to clear a default app has been discussed here at length, but what I am trying to do is set an app as default. I defaulted the standard messaging client but have decided to replace it with Handcent, but the popup to set a default no longer appears on launch of either the standard messaging client or Handcent. I have cleared the default launch from the messaging client, reinstalled Handcent, and rebooted, and no combination seems to work. Anyone have a tip/trick for doing this? Thanks!