[What's_nitro?]

Unless the shock of the landing causes the LiPo to shift and coincidentally dent/puncture/tear itself on another part of the vehicle, then no, hard landings are not bad for LiPo's. Make sure there are no possibly sharp points within the battery tray. Or just make it so that the LiPo cant move at all. I think you're all set if you have it surrounded by foam already. Just don't go landing squarely on a rock when you're out bashing.