Greg,
The stock Super Cub will not take off from grass with a 7 or 8 cell battery, unless the grass is really short....It will land ok as long as you remember that full up elevator will drive the tail down.....I say this as the first thing all complain about is that the plane wants to nose over on grass landings. The truth is that if you apply enough power to fly it, and fly it to the ground, the minute it touches down the grass will want to stop it. At this point it will not have enough airspeed to take off, but if you give it full up elevator, it plants the tail and avoids nose over.
Taking off, with the 7 or 8 cell NIMH batteries will almost require a hard runway. Later on you will find mods that will enable grass takeoffs. Pat