I’m replacing the extractor fan in my kitchen with a cooker hood which will be placed on an internal wall. There is already a large hole trough the external wall where the old extractor fan went through. It’s positioned in an awkward place so was thinking of running a flexible duct from the extractor and into the ceiling and hoping to then use a rectangular duct and 2 L rectangular to circular connectors and run this down the cavity only by about 20cm and to the existing vent. Was just wondering if this would work okay?