Orian Dorado passing cable through rear body

Hi all, new here so hopefully correct forum.
Just changed backed to motorhomes after 10 years in caravans and picked up my Orion 2007 2.4 Transit yesterday from Somerset Motorhome Centre.

I want to fit a rear camera, as I have figured out from here you cant remove the rear high level brake light (bad design Autosleeper!!)
So I need to drill into the shell just below it.

Does anyone know if there is a gap running between the fibre glass and the internal wall below the high level brake light and the rear window that I can pass a cable through and down and out of the bottom of the van for the camera cable? Or will I hit the void full of insulation?

Hate the idea of drill straight through the body!!!

Many thanks.