I'd reduce the bracket at EC for B to at least 1:41.8... then C can be from there onward. I reckon on any given race meeting (assuming it's dry, not too cold, not too hot) most riders will be in the high 40s to mid 45s, so there has to be a split there otherwise you'll have 20 B graders vs 5 A graders and 7 C graders. Plus we all know the faster you get, the harder it is to drop time... the difference between 45s to 37s is an eternity and most will never get there I think. From 46s to 41s however, is not impossible and with enough racing, most ppl will get there. But it will take experience. So to me it makes sense they become B graders once they get past that.

Also, no brackets for D? Not sure I understood the proposal then... Thought the novice would also serve as a way to get ppl into the right grade after they served their time? I'd put a C bracket of 41.8 to 46.0 and D grade if over that.