Your bow was probably designed to be shot with your fingers next to the nock, either using the split finger or 3 under grip, so there should be no problem gripping it there, in a direct answer to your question. There might be a slight tiller adjustment between split and 3 under, which is easily accomplished on ILF limbs. As was stated, if the only thing you do is to move your grip to the nock, your POI will be higher at 20 yards, and changing the tiller won’t move it back down where you want it. The POI of your arrows is determined by the weight of the arrow, the bow weight, the length of the arrow (if you aim using the point of the arrow), and the relationship of the nock to your eye. So far, you have changed the POI by using a fixed crawl, which brings the nock of the arrow closer to your eye. You could move your anchor up so that the arrow nock is in the same place it was when you used the fixed crawl, and the POI would theoretically stay in the same place it is now. I and others have tried a high anchor, and nobody that I’ve heard from really likes it, but it doesn’t hurt anything to try. I also don’t like any of the other alternatives I mentioned above, but you’re welcome to try them too, because they have worked for some other people.
What I do like is a technique recently discussed on the Form Forum by Rifleman, which is gapping off the riser. By cutting the top of your strike plate to a certain height, you can use it to set your point-on to 20 yards, or other distances as you like. You grip the string at the nock, as many of us would prefer to do. Once you start gapping off the strike plate, it doesn’t matter how long your arrow is, as that no longer has any affect on POI. Hopefully this link will get you there, if you’re interested
http://www.tradgang.com/tgsmf/index.php?topic=164996.0