Monte Smith always said that eventually you get to the point where you start bending housings...with a Dana, there's nothing you can do to stop it.
This is less likely to happen with really narrow housings like on a big tire car (depending on the power level of course). On a small tire car w/ stock style suspension (wide housing), especially on a drag radial, this is more of an issue.
I talked this over w/ him and he advised me to keep an eye on the housing and when (not if) it bends, to bite the bullet and change rears. Keep in mind, he's not talking about a 700 hp bracket car on slicks.
Every part of a race 9" is aftermarket, so the stock 9" strength argument need not apply here.