Have not myself, but read of it happening to more than just you. Too bad you didn't happen to fill it while under warranty.
I imagine the tank spread the support angles as it filled and dropped down between them. If it is on the axle, you should be able to get it back up without too much trouble to take to a shop. Needs some sort of support underneath it, not just at the edges--many of them are sitting on angle iron straps that are pretty flimsy.
We have a 100 gal tank and travel with it full lots of time and no problem.
'05 36TK3 Mobile Suites
'10 F450 new to me
'09 F450 Lariat 4x4--died