Exactly and you should have been practicing this prior to the season but now it's time to practice it. Clearly if you had your 20 yard pin high on the animal, the arrow would slightly drop under this, if your 30 yard pin was low on the animal, the arrow would go higher than this. I use the 20 yard pin slightly high and use the pin gap as a "pin" as mobowhuntr mentioned. I practice this and know how/where to hold the 20 yard pin, at this point my 30 yard pin is also on the animal. I know my arrow will hit between the 20 and 30 yard pins on the animal. This should get you close so you know how to start your practice session on perhaps a 3D animal.

Good luck.