I bought a stronger spring from Amby when my DS1 would bounce so hard the hammock nearly hit the floor (he was getting close to 2 years old though!) and the stronger spring snapped . Luckily I was holding it so I caught it before DS was hurt. I contacted Amby and he sent me a new spring and it never happened again. I also used to keep a small foam mattress under the hammock just in case.

I think the issue for us was that my DS was that much older and he would bounce himself so hard!