Symmetry

Back in the day, it was nice to put dual fuel tanks under with dual stacks... Symmetry could commonly be achieved with batteries inside the cab, between the rails, or moved to the headache rack.

Today symmetry of fuel tanks is difficult to accomplish. Dealing with the DPF/SCR/DEF components of the aftertreatment is a real challenge. Batteries LH under cab with DPF/SCR in the RH position provides a fairly balanced under cab.

Symmetry today is often forfeited to practicality.