The XR is the chassis that's used for the 1200 4 tec Engine and the tunnels do vary in length depending on the model. The ski width is the same as the XP but the 4 Stroke engine requires more width which gives the XR a wider appearance. Also the A Arms and cross members of the front suspension are bigger in diameter on the XR. I assume that is because of the added weight of the 4 tec. So yes, it would be a stronger chassis based on some of the components.