If you do top it's best to get them when they're very young so the split will be low and it gives the plant plenty of time to recover. I usually pinch off the 4th or 5th node as soon as it is pinchable. This way you can train both stems resulting from it to grow in two opposite directions. Once several inches have grown on each stem I take a 1" thick strip of duct tape and wrap it around the trunk where the split begins to stop it from tearing once the training begins.