Crisp is a premium theme and premium themes are supported in the premium theme support forum by the theme team and the theme author. We volunteers in the main forums have no access to the premium themes so we know nothing about them.
CSS questions for premium themes can still be posted here. If it’s a question that cannot be answered by looking at the site or by using browser tools like Firebug or the web inspector, or if it’s a question about the theme functions themselves, that’s when you would want to go to the premium theme forum which should be linked in your Appearance → Themes page if you have purchased a premium theme.
If you want to change the header height in Crisp, you can absolutely do that with CSS like this:
I see you’ve already made some modifications including the height and it looks beautiful!