L332 G4 type Roof Ladder fitting

Hi Guys

Has anyone fitted a G4/G4 type roof ladder to a 2005 L322 - found one on ebay, no fittings or instructions.

Unsure whether to drill the holes and struggle with interior, or use riv-nuts and leave interior well alone.

Has anyone else fitted one, and which method did you use?

Thanks Peter

Good question as it seems, maybe the Australian forums or the American forums could provide some info you