: The cupping is probably caused by the feather edge bending down as
: the plane passes over it. You need a firm base to work on and a
: sacrificial piece of similar material underneath.

Thanks. I will give that a try. I had a decent working surface, but as you guessed I didn't have a sacrificial piece. I also didn't notice that the other side of the board wasn't fair because of a tear out on the milled edge. I'm also going to try a longer plane (I was using a block plane) for the initial part so that the back of the plane stays on the top board when the blade hits the bottom board. Thanks again.