You don't know how hard I'm trying to avoid having to, but you asked nicely [enough].
It won't be instantaneous. My choices are a Sharpie sketch snapshot or a new program, Krita. Maybe time to learn a new program.
For now here is a bellmouth. They are mostly round or oval but they can be rectangular
http://www.ductdirect.com/SpiralPipe...tsSpecs/BM.gif
The outer half rounding into an air curtain needs more hand-waving. Here's a box cavity:
http://www.curbsideclassic.com/wp-co...mage/28078.jpg
IIRC 20-->24MPG.
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.Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
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.Three conspiracy theorists walk into a bar --You can't say that is a coincidence.
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