Bill Jenkins used epoxy-coated wooden stuffer plates in the bottom of early SBC tunnel ram in 1970 to proportion plenum volume to engine size, he felt the stock manifold was too big for anything less than 380".
If the triangle is not completely sealed I doubt mixture would go through it, but it would still be a buffer volume damping vacuum.

The MM appears to make the plenum width almost match the flange pattern, but it doesn't need to for NA.
If the plenum box were taller, the sides could taper inward. Then make the box narrower and add the length to the runners. Something like this may be possible as surgery, but I'd rather try it on an old Offy than the $$$$ MM.

For blower use, of course the top comes off, but any Roots with helix rotors does not have uniform discharge along the length of the exhaust port. The highly developed Kobelco etc. port is a long triangle closely resembling a NACA duct.
Most of the volume enter the first 4 cylinders, and none at 7 & 8. A mask between the top and blower case can correct this at minimal cost.