Cracks in the floor of the tub are not common by any means, but they have occurred. I would have no confidence in any simple repair, because the bottom of the tubs flexes when you put weight on it.
Several years ago, we had a thread on this topic, and one of the suggestions was to put some blocking under the floor of the tub so it can't flex. I don't know how it worked out, but I will try to find the thread and add a link here.
EDIT:
http://www.trailmanorowners.com/foru...ad.php?p=41081
By the way, how did you decide to post about the tub in the
Getting Started on the Board forum, rather than in the
Plumbing forum? As a Trial Member, you have access to both, but I am always concerned about the forum definitions that we provide.
Bill