I wouldn't say a pusher config would aid in rudder control. Prop wash from a tractor config would make the rudder more effective at times of high angles of attack. If you are using a pusher, a sub fin and rudder would be a good idea I would think. You may have diminished control over the rudder but your elevator and ailerons should remain responsive. I think you should be ok. What is your canard area versus wing area look like? The canard looks a little small from just eye-balling the pic unless you are making it to where the entire canard fin rotates.