Here's a picture of one ... they're quite readily available, and the price dropped back to 'reasonable' a year-adn-a-half ago.
I'll be damned..just when you thought you'd heard of everything.
Uh, what does it do to the CG?
Aftermarket? Or ComBloc?
Not even supposedly knowledgable folks seem to know this.
< /Pet-Peave Rant>