If you want tough, you might want to consider the A123 cells. Lipos, even the ones in cases, are still relatively easy to damage.

I run all of my lipos in either aluminum or carbon fiber trays that leave nothing exposed but the top of the battery. I also got some foam padding to put into the front of the battery trays to add some protection in case of a frontal impact. I then use velcro on the packs and a strong nylon strap to hold the packs in the trays. I race and bash really hard and destroyed a few lipo packs trying to find a system that wouldn't let go of the batteries in a hard crash.