Changing default messaging app

[Spikelangelo]

My gf started using Handcent and likes it better than the built in app. Even though I've disabled notifications, the built in messaging still gives a notification duplicate. Second issue, there doesn't seem to be a way to actually change the default messaging app to Handcent at all. I've tried the built in option on Handcent to set as default but it still doesn't work. The annoyance is the lockscreen and the launcher can't seem to be changed to Handcent or anything for that matter. Has anyone been able to do this?
Worst case I'll have her switch to a new launcher and freeze the stock messenger, but id still like to be able to change the defaults.

Edit: phone is rooted

 

[Spikelangelo]

Update:
It appears that the messenger app links are hard coded. I removed the messenger app with titanium backup thinking it would switch to Handcent automatically or at least give a prompt on what to use. It did not. It would freeze temporarily and reboot. Ultimately I had to switch launchers and also install Go Locker to prevent from swiping the messenger shortcut on the stock lock screen. I also had to leave the messenger uninstalled (freezing works too) because there is no way to prevent double text notifications. There is a checkbox in the messenger settings to enable/disable notifications but unchecking it does not work properly (it doesn't hold). You will still get a notification except when tested immediately after unchecking it.

Also note that I did try a number of apps off the play store to change default apps. The phone does not allow setting defaults for some of the features, one being the messaging app.

It's just a work around but I thought I'd post it as there appears to be no info on this topic.