Boy gets girl?....that's just fabrication.(see feeling dim) ...and onto fabrication of another sort ...
Following Azzazellos measurements I first made a paper model. Now in process of making a stiffer model from depron (pizza base packing) looking at the underside of the dashboard I can check the shape out. It's easy to see that these duct things are handed. Asymmetric -smaller on the outside sides than the middle sides.(tapered) So Paul you are right they cannot be swapped left to right . More tomorrow I'm off to bed completely knackered.