The horizon is not necessarily too low.
Where to place an horizon, either in-camera or in post-processing by cropping, is always a horse-for-courses decision since by changing its placement it obviously changes the entire feel of the image and how it is then interpreted.
In your case the fact that the clear sky dominates the image in the way that it does reflects an aesthetic statement by yourself.
The question, in my humble opinion anyway, does not then revolve around whether I think it is right to place the horizon where it is but rather what you are trying to communicate in your image given the placement of the horizon.
Compositional tools are just that: tools. They are not rules that you are bound by. Use compositional tools to build your artistic vision.
It is true that not all compositional tools play well together so how to combine them takes some wisdom, some experience, and ultimately a lot of artistic horse-sense.
Perhaps it is worthwhile reflecting a question back to you: Do you think that you have achieved your artistic and aesthetic aims in this image?
I think the answer to this question may well settle your question to me.
Tony Jay