It's a tricky one, having Naismith in the middle of the three does make us more vulnerable defensively as he's ok in the air but not great and can make mistakes. However, in the middle I think he's better placed to make the passes that will set up our attacks. We just need to not be so predictable with it and not have him start every attack, that way teams will push two men on to him (like QPR and Norwich) and it'll be impossible to get out.
It might be worth trying him in midfield but I have a feeling he won't be any where near as effective getting the ball with his back to goal and would end up dropping so deep he'd end up on top of the back 3 or 4