aerohead -- Thanks for giving this your attention. I'm looking at a die-cast scale model and it looks like a [no more than] 4" inverted U-shape leading edge for an airfoil.
Given, say, 250cfs of flow (25 times 10x) through the duct what should it's area be? I'd address the slot opening later.
I'm comparing a minimalist vertical hoop with something more like the Bird of Prey:
https://nationalinterest.org/sites/d...s/boeing_0.jpg
I think it could have an angled intake throat if the plenum is fed from the quarter-points instead of the ends.