Again, I would not worry about that. Coticules are pretty hard and wear very slowly compared to synthetic stones in my experience. The wear would be somewhat uneven regardless because you would presumably be doing an X pattern stroke and not honing on all parts of the stone for the same length of time anyway. A periodic lapping with a straight lapping plate larger than the coticule will even it right up if you hone enough razors to need it. If you already had the right tools and experience to cut you could certainly do so (at risk of damaging the stone), but if it was me I would just go the easy route and leave it as is and buy a slurry stone separately (which should be pretty inexpensive).