r00g - the bouncing around is funny! I like to go full speed across the grass (in front where there is a lot of room) and watch it bouce around
4wdmt - No, the 4200mAh capacity only has to do with runtime. The higher the capacity, the longer it will run. BUT, newer batteries are more powerful than old ones. And 4200s are pretty much the newest NiMh batts you can get. They have super duper punch and power. 3600s and 3800s have mad power too. I think any IB cell (3600, 3800, 4200) that is fully charged will wheelie a stock Clod if your ESC doesn't have current limiter built in.
My old charger wasn't fully charging the 4200s. It would take like 45 minutes at 3A. Now it takes 67 minutes at 4A which makes more sense if you think about it mathematically. 4A charge should charge 4000mAh in one hour. My 4200 acutally takes 4300-4400 mAh according to my charger.