They probably recommended against it due to the weight difference, as the 'vert is about the heaviest Fox made. Putting those under a 'vert will probably lower it farther than the original specs intended, but probably nothing too drastic - maybe 1/2" difference? - so it depends on how much of a drop you're looking to achieve. Stock Fox ride heights aren't exactly 4x4-like, so be careful how low you go, especially with an aftermarket H- or X-pipe of any kind and/or longtubes...