scaling of kneading when scaling bread recipies
When it comes to kneading, scaling partially depends on your physical capabilities. It's a physical activity, you may not be able to manipulate double the dough in the same way. If you have the arms of a gorilla it will probably take far less than double the time, if you are on the weaker end of the scale it may take you longer than twice the time as you might have to get it partially kneaded and then split it into halves to complete, or you simply tire and slow down. 

The message here is to knead for a result, not a time. That's actually one of my primary pieces of advice when bread baking in general, and not just kneading. Knead until you get the texture you are looking for, no matter the time.