White over black is always tricky. Even over grey, it can be difficult. When I did my Hudson's white over grey, it took more coats than I would have preferred. I think in the future, for large areas of white, I will prime and paint with white and then rely upon oil weathering to tone down the white areas so they are not so bright. IN your photos, it looks like you might want to add another coat, mainly to reduce the "greyness" factor. No reflection on your work as it looks great.
