I said not chamfer the edges of the keel (end to end), because later in the series the real keel will be fixed to it, if you do, you'll greatly reduce the contact area for gluing the real keel to the frame keel, and more importantly the real keel could rock from side to side rather than sit, though at some point along the way the keel at the stern will be tapered where the frames rise.

Best rule of thumb, unless your pretty sure of the build then don't do anything outside of the steps, obviously any improvements are down to personal choice and an understanding of the design so as not to get yourself into a pickle later on.