You know what is surprising? You have built something and it actually works the first time. My groups sphero penny carrying creation worked. We didn’t have time to actually put any pennies on. But at least we know our way of attaching the cargo carrying part to the sphero works and floats. It may move a little slow, but the water we were testing was too shallow. So, our attachment method was dragging on the bottom slowing us down. Our attachment is currently not mentioned by name.