Fitting a Bulkhead to a Vivaro

Hi I am about to fit a factory bulkhead to a Vivaro thats never had one.

I have noticed that there is plastic trim covering the screw holes on each side walls.

When looking at the inside of the trim there is a raised mark going down the trim, is this a cut line to modify the trim to fit a bulkhead?

any other tips on fitting a bulkhead?