I've been serching LC and doing some thinking about this. My former plan was to place them parallel to the sides of the neck. The line of thought is that they will better add reinforcement and stiffness if placed following the real direction that the strings run and closer to the edges, where especially the lower strings generate more tension. On the other hand, placing them like that will cut the grain of a bigger area (and volume) of the neck than when they run parallel to the TR. So I'm in doubt which way to go. In my case the neck wood is wengue, so making it weaker and then add the rods to reinforce it seems somewhat contradicting. But still I cannot help thinking about the the tension that the edge strings apply to the neck. What are your thoughts on this?