I was getting tired of dragghing my ERevo back home after these arms break, and in my experience these are the weakest parts of this car. So I modeled a temporary replacement, so that I could swap a broken arm in field and keep on driving (more carefully, though, since these are certainly weaker than stock). 

To address the layer delamination when attaching the arm, the model intentionally has some gaps. If your slicer is configured correctly, the printer will fill those areas with perimeters, making them stronger.