Always check never assume as curl doesn't indicate always a split. How ever, from what I've read and seen if they are curled or unusually long in appearance they tend to be at a higher risk for having it...again or so I've read. I'm more of a if they have it genetically speaking they have, curling or length doesn't affect it directly. You should be able to at that age look and see if there is or isn't a split; if you have trouble pop in a doe (but don't let him actually breed) and check him while he's excited. If he does, since most tend to lean tend a genetic issue although some think it can be enviromental (I don't understand how but part of what I've read in general searches), would be best to cull from breeding. I've heard some boards/sites say that they can't or usually don't produce a litter but when I first started and got a bad line of fuzzy lion heads and just didn't know any better they had no issues with producing. Once I found out the whole line was culled though. I got a completely different line and never had another issue.
Google can turn up plenty of pictures of splits as they can vary from just slightly to all the way down to the base.