I saw years ago where Rich Ehrenburg (sp?) tried the Vanke-like mod on a BB 6-BBL intake... didn't go well, as I recall. His attempt cut basically the entire divider from each 2-BBL plenum.

Before he did that, I did a less extreme version on my 440 6-BBL intake that picked up a little on the track, without hurting streetability. My approach was to lower the dividers similar to an Edelbrock Performer RPM for a BBM... maybe a little lower. Track improvement was .5+ MPH, not huge.