I am putting it on a mutation X V4 RDA I wanted to build a parallel dual coil with 26 gauge Kanthal how many double wraps should I use for each coil for optimal results?
Hard to tell what optimal would mean for you, depends on the type of mod and your personal preference.
You can use this calculator to help you figure out the resistance of the coil: http://www.steam-engine.org/coil.asp