TC, one of the main points of the fixed crawl is to use the same anchor you normally use, so you don't have to re-think too many things in a hunting situation: just move your grip on the string down under the fixed crawl nock and draw to your regular anchor. As a split finger shooter, I guess you would also have to get used to drawing the bow without the feeling of the arrow nock between your fingers. There are a few other differences anyone has to get used to, such as having a different sight picture, etc., that are mainly psychological. Before you go to the trouble of tying on a new nock, I would just play with it for a while, and grip a little below your regular nock, as Dennis says, and notice where the arrow hits when you place the arrow point on the spot. You should pretty quickly get an idea of about where your fixed crawl nock should be to get the point on distance that you want, and can fine tune it after you tie on an adjustable nock.
You will essentially be switching from split to 3 under when you use the fixed crawl, and then switching back again when you use your regular nock. If you can adjust to that, fine; if not, you could try moving your anchor rather than your nock point. You would still be changing just one thing, and would be shooting split for both aiming points. For example, if you now use your middle finger in the corner of your mouth, you could try using your ring finger, or just getting some new anchor altogether higher on your face. When I tried this, I developed a pretty good anchor using my first two fingers on the top and bottom of the bone under my eye socket. Another advantage of this is that it would still be legal in some tournaments that forbid string walking.
I have been doing quite a bit of experimenting with both the fixed crawl and using a different anchor lately, and am actually leaning in the direction of changing my anchor point rather than using the fixed crawl, since it would be legal in the tournaments I shoot. Both seem to require about the same amount of psychological adjustments to get used to.