First of all, you did a great job!
Now...
I have seen quilts where the side borders are different than the length borders, and they look nice.
You may also consider shortening the length (on each end) and adding a wide border all around. If you do this, the log cabin design is on the top (horizontal) of the bed only. Expanding on this thought, after shortening, you could have log cabins in the corners as part of the borders.
Good luck, and let us see what you decide.