That sounds like it would be very difficult. You would have to have the skills of a professional diver to pull this off.
If you're absolutely settled on jumping, I would focus more on finding a spot that is high enough so that it doesn't matter how you land.
Try this
Free Fall Calculator. It allows you to calculate the top speed your falling body would reach if you jumped from a given height.
Just put the height of the highest building you have access to into this calculator, and you can get a rough idea of what the impact would be like.
Also, hanging as a method is far more reliable than jumping; Jumping is a coin toss; you could die instantly, or you could spend several hours writhing in agony only to recover and become a ward of the state. Both partial and full suspension hanging are basically guaranteed to cause unconsciousness within a few minutes, and kill you within half an hour as long as your not interrupted; still a painful method, but you have some idea of what your going to experience, whereas jumping is completely unpredictable.
I would really spend more time on the forum looking at more attested methods before you try this. It's not a good method.