Holy sagging water tanks, Batman!

I wish I had found this tread last summer when my Winnebago Lite Five bottom fell out a thousand miles from home and the dealer. Winnebago said there wasn't a board for support but the flanges you describe. The dealer finally "repaired" this after I limped home, waited a month for an appointment, and took a month to get it back to me. There was a board and the repair indicated that the whole thing was installed wrong. Now, no one at the dealer can describe how it was actually repaired. We did have algae or some kind of growth in the vent hose a few months later. So, your posts indicate that that means the vent hose was repaired with the broken bottom incorrectly. And, did I mention that the black water release valve leaked mightily at the same time? That took the dealer two tries to repair properly (or at least so it didn't leak).

Here's a question: I still have a sagging belly (the trailer not me necessarily). Does that mean there probably isn't proper support up in there. I keep a couple of straps across the exterior to help. But I'm worried.