Our teacher have always emphasis the importance of syncing motors ( For parallel arms and so on ) . However this spoils most of the 269 motors .Definitely placing c-channel will help but its very minimum. Do your have any suggestion on syncing movements of arms ?
What we found to work is to have the idling gears share an axle. So if your arm has a 5:1 ratio then on the 12 tooth gear have an axle connect both sides this makes it so that one motor cannot get that much out of sync from the other because they share a axle.
I’m not entirely sure what you are asking, but whenever my team wants to put multiple motors on an arm, we gear all of the motors on a side together and then attach the appropriate gear to the arm joint.