[Whaler]

Tim to interupt any side you must be switching upstream of the destination path.
Therefore you have to basically open up the ground path ahead of all the downstream grounds

Which gets back to being close to the source, the battery.
Most people use 2-3 big grounds ( I do)
One immediately from batt neg to frame.
One from frame to engine block
One from a starter bolt or bellhousing bolt to frame as well.

So where the battery sits may be a consideration when these multiple paths must be isolated, so the car can no longer offer a grounded side to an unswitched positive side.(the hazard)

You want to have opened up the negative side netween the batt and all 3 of these grounds....Thus offering no potential to the positive/s