While there may be a break group that can hold on to the stage, the prevailing headwind in the area means any team could easily pull them back in if they are willing to work. The main focus of the stage will come down to the final 20 km where riders will twice ascend the Cat 3 climb Mûr de Bretagne. While the climb is only 2 km at an average grade of 6.9% there are steeper sections over the first half of the climb. GC riders will be eyeing each others fitness on this climb and someone may try to make an early statement by attacking on the first pass up the climb then push the descent before the final climb back up to the finish. To give some perspective on the type of numbers riders might climb these types of grades we can look at data we have seen from the Giro. A rider of Dumoulin's size (70 kg) sustained around 395-410 watts for some of the longer climbs. That would equate to roughly a 5 min climb over the 2 km. If we were to adjust the weight down to a Chris Froome or further to a Quintana size you are looking at 370 and 360 watts respectively. Watts/kg however would be lower for Domoulin versus Quintana, but at these gradients (and most seen at climbs in the tour) there is a balance between Watts/kg and FTP that starts to favor a rider like Froome who can over power a smaller rider and out power to weight riders with higher FTP. Get additional Data-Driven Coverage of the Tour on TrainingPeaks.
We modeled the peloton as a single rider using the typical pulling power exhibited by riders at the front of the main group. Try using the Time Analysis Tool to find sections on each course where different types of riders may have an advantage. For example a lighter rider with slightly less power will show gains on the climbs.