[Varley]

At least you know where it is coming in. All I know is where it is coming out!

I wonder if you might stretch your skills beyond steel trays (much though a welding opportunity is to be welcomed) and consider motorising the whirly vents and controlling them with a rain detector. On recognising rain they would start up and throw off the water like a clear-view screen. Of course there might be the risk of them vacuuming up much of the contents of the bijou res. (pets, ready-meals, flagons of the foaming, guests etc.) and hurling it, creatively mandolined, about the neighbourhood. By dint of giving each variable speed drives it might also be feasible to produce something more tuneful than rag time.