I would not get too concerned with points head heavy or head light right now. Rather, go with what feels right. So that you don't waste lots of lead tape, you can attach it with finishing tape during your trials. This way you can even move the weight around while you are at the courts and find the right fit for your game. When you've found the right fit, then it is time to start taking measurements. These measurements will enable you to customize another HEAD i.X5 OS racquet so you’ll have a matching pair. You will probably find that the second racquet will require a slightly different amount of weight to be added to match the other (you may even have to add some weight at 12 or 6 to match balance), unless you are fortunate enough to start with two identical racquets.
When customizing my own racquets I always go by feel. When all is said and done, I'll measure specs.