Topic: wire routing


I am working on the wiring of my JJT Contessa 26.
The diesel is Farymann
The original wiring was modified with addition of the second panel.
My question is: How routing should be done properly?
The tricky part for me is bringing power to both panels.
It seems I can not avoid but route these wires trough engine compartment.
And on top of this having a negative bus mounted on the side in the engine compartment will help too. Are these bad ideas? 
I need a routing/physical layout schematic.