I think your logic there is fine. My area doesn't have hills quite that steep, fortunately.
I have good luck growing on southwestern slopes if the right amount of shade is there. The roots might not grow as fast...but that isn't always a bad thing. I've grown ginseng next to my porch in town with a western exposure. I planted some cinnamon ferns in front to provide shade when the sun got to that side of the house. So, I believe that some areas (NE slope) might be ideal, but never ever give up on what you have too easily.
Test plots are wise and I commonly suggest that to my customers.
I can't say where I've had good results in growing. However when hunting for it I have been on ravine sides that I had to hold on to saplings with 1 hand and dig with the other, because the sides were so steep. On the otherhand, at the top of the same ravine the land was relatively flat, and it was also growing. I think if the soil is right and the area is properly drained, the slope is not a critical factor.