I would start out with carefully measuring your stock ride height on a level surface, so you have a reference point (assuming the car is still stock). I would also mark these reference points (masking tape) and use a hanging plumb line (weighted string) if you are going from the center of the fender arc over the tires. Sounds picky but an eighth-inch error here and there does make a difference, especially if you are
not planning to do a corner-weighted alignment (which most shops don't do; there is one shop here at nearby Infineon Raceway that does it for $300).
With stock sidewinder wheels & PS2 (stock size) tires I went lower by 7/8-inch in the rear and 3/4-inch up front. Car looks lower but not slammed. A number of established Viper specialty shops use very similar lowering numbers. You may be able to go slightly lower than this before the tire starts grinding the inner fender liner when bottoming the suspension. I'm not into that. Also, with stock sized wheels, I find that it looks somewhat odd to have the fender nearly at the tops of the tires and meanwhile have large gaps at the front and rear of the tires (to the fender). Going to a larger rim set (like 19/20) fixes that little issue.
Mo' money.
FWIW, this amount of lowering came out to 26.5" front and 28.25" rear as measured at the center of the fender lower edge (centerline of wheel).
For damping, only the rebound is adjustable on the V2s. KW recommends starting at 9 clicks out from full firm (or 1.5 turns on the adjuster). This is just centered on the range, if I recall. The general consensus from other KW users is go more toward full firm (say 3-6 clicks out). Some here even use full firm, but... ride quality is a matter of personal taste, YMMV. I just set mine last nite to 6 clicks from full firm and if it ever stops raining I'll let you know what I think.