Power distribution block mounting

[Kapao69x5]

I would appreciate any sort of help at this point, since we are in the process of re-wiring our electrics.

How exactly do you mount the power distribution blocks on the DIN rails? I assumed since they came in the same bag in the kit of parts they have to to used in conjunction. (Even though my physics professor denies it. )

Also, following the 2007 power diagram, I noticed 3 of the four negative power blocks leading to a CIM motor (the kind we are using for driving), while the fourth one leads to to fuse box. My question is, do we need an extra negative power block or can we use a negative common and split one of the wires and use it on the fourth CIM. I find that solution very unprofessional but with the limited time frame until shipping the fifth block will have to wait.