I look at the viper calipers once and a while, but I'm really unsure if the opposed pistons have any chance of clearing my Torque Thrust M's. It's somewhat difficult to offset the rotor far enough in for the caliper to clear.
Assuming I have the correct rotors, looks like the Cobra rotor is about 5/8" from the front of the rotor to the wheel mounting surface, while the rotor Dr. Diff uses in his Viper kit is about 1 3/4" from the front to WMS.
I've got an '03 Viper rear caliper here and I think the body is the same as the front but with smaller pistons. My eyeball measurements off that say the caliper is about 2 7/16" tall off the front of the rotor if the caliper is centered over the rotor.
So, with the additional 1 1/8" gained from the deeper rotor, you would need about 1 5/16" off the front (outside?) of your current rotor to clear the Viper caliper.
There is certainly more to it than that, but maybe it would give you something to make a guess with.
