Is logo size not affected when using Navigation as Header?

Hi there, I'm using Navigation as Header, and the logo is very small, even with image size larger than the suggested image dimensions: 350 by 70 pixels.

Is the logo size options not working, when using Navigation as Header?

A comment to the topic on centered logos, I see a lot of centered logos on mobile app's, at least here in Europe, also Twitter has a centered logo on mobile.

This look has inspired me for my site, and I expected it not to be a difficult task to achieve, but could be done with a flex box, but apparently it is not that simple.