[freebeard]

It doesn't matter how the elongation and taper is executed,but the trailing edge must to be continuous and airtight,wrapping all the way around as Kamm has done,or as with a sealed box-cavity.Any 'hole',anywhere, will allow lower pressure are to bleed into the space and adulterate the pressure increase you're trying for,netting low to zero gain.It's not negotiable.

I'm not sure what you're saying here. Holes to the upstream exterior, or to the interior?

Open box-cavities OK?