Logo in full size ?
Possible Answers to Your Question:
To maintain integrity of the header, especially in sticky or overlay mode, we limit the max height of the logo to 255px and the width to 300px. (should be scaling to width, not hard cropping).
Additionally there is limit to the height of the header itself. You can remove that limitation with CSS:
You will then need to adjust the container padding on the widget area if you are using Overlay