Yep. Just rename it. I personally need a much longer tone for SMS. With the phone in my belt clip I frequently didn't here the short default notification, nor the shorter reminders. Sure if I'm staring at the phone when an SMS come in it's a bit long, but the important thing for me was to not miss 'em.
To each is a time and place . . . (Haha
One more thing. If you like the sound but the length is too long, you could change the extension to aif, copy to iTunes, edit to shorten it, copy back, change the extension back to caf and have a shorter version. That is how I created it from the original.
