The back light to my skid-plate is using two pairs of 10" Rigid Cool White Strips but it would really depend on how big of a space you are backlighting.
Larry had two 12" Flexible-waterproof strips used as rocklights (in between the front and rear tires, under the doors, not the ones under the front or rear bumper) on each side. I used three on each side.
I would also want drive shaft, rear axle, and each wheel well, front and rear bumpers. sounds expensive.