Hello all. I am baffled and need some help. I recently bought a 2017 Acadia All Terrain with only 19K miles. It is in pristine condition. When I was washing it the other day, I looked underneath and noticed these channels welded on to the floorpan/frame on both sides. I know that models with separate rear A/C have refrigerant lines in protected channels leading from the compressor. I don't have rear A/C, and even if I did, the lines would only run along one side. The channels are u-shaped with lightening holes on the surfaces that face the driveshaft. Does anyone know why these are there? They certainly reduce ground clearance.