You've purchased it, installed it, and probably aren't returning it so this maybe a moot point, but I'll elaborate none-the-less. True drag cells are assumed to be installed on a fully caged chassis running only on the strip. You almost never have a rear end collision on the strip and if you do, you have a triangulated cage.
http://www.fuelsafe.com/white_papers/fuel-cell-facts.html Fuel Safe has some good research and white papers on the subject. We have 2 Lemons cars that both have ATL cells that cost as much or more than the car. Now you don't need something like those (one of our cells is in the front of the car, and the other is in a 2 seater right behind the driver, so containment is key) but the stock tank is about 3/5th of the way down the car and has a lot of metal to absorb and deflect a massive impact before you get to the tank. In your case now, even if you only drive this car on the weekend or to the track, this
http://www.yenko.net/ubbthreads/ubbthreads.php/topics/503657/Re_Friend_in_Accident_Leaving_ can still happen. Even with foam, those cells just tear apart on impact, throwing gas everywhere. On a bladder cell, the metal or plastic deforms/breaks, but a very high quality bladder squishes around the impact. I've seen MASSIVE rear end impacts road racing (either on track or getting hauled off) and I know those cells played a huge roll in these cases.
That's my input.