0.4 mm Pitch BGA stencil design

I've searched the archives and maybe my search skills aren't up to snuff but I couldn't find much. I'm curious what people are doing for 0.4 mm pitch BGAs, assuming a type 4 paste.

Pad diameter? SMD or NSMD? Stencil thickness? Aperture diameter? Using step down stencils?

I've been playing with different designs and I'm having a heck of a time finding a balance between shorting from too much paste or apertures that are too small for consistent release.

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