No i don't. They seem legit. Maybe do a search or ask in the more mod-friendly forums such as the Legacy/WRX/STi ones. They[xcceleration] have mods for all Subs so someone is bound to have dealt with them on those boards.
I'm comfortable with the center of gravity the stock Baja gives us. But if someone does end up opting for this kit, let us all know how it worked out.