I'm jealous and applaud you and your effort. Just one thing... you say you wanted it difficult but the lanes were too narrow. Leave the fast areas wide but narrow it down in the technical areas. A driver should be running on a 2-3 foot wide lane and even less in the corners. If you are racing competitvely and drift a few feet wide you will be passed or at least make the lap times slower. does your dog get all uppity when you don't let him play too?
Post up some videos, we love this kind of stuff.