take 2 small thin sharp wedges,,tap them in the grain you wish to follow,one on either side of stave and in the same earlywood line,once its starts go slowly and hope for the best, this is not an exact science,sometimes it will follow it great sometimes it wont, you dont know till you try,either way it cant ruin both staves, so you will have one anyway, but you might have two, it is worth the risk, I can post a photo tomorrow if you like, I split about 30 staves today, and my inside splits ran about 50/50