I tried that on the front outer pin, but broke a front arm once. I think the bolt/nut holds the arm together better and keeps it from spreading and breaking.
I am not sure what my truck weight is. When it was box stock it weighed about 10 pounds 3 ounces. But I think it is closer to 9 pounds 9 ounces now with a bunch of light weight screws and stuff. I am using a lipo now also.