Jira Service Management Portal Banner Size

We’re in the process of building out a JSM portal and widget. My design guys are happy with all the content, but hate the huge banner height. From looking I can’t see any way to change it through Jira. But on searching I found some Atlassian images that appear to show a much smaller banner.

https://developer.atlassian.com/cloud/jira/service-desk/customer-portal/

Does anyone know if there is a way to modify it?

Thanks in advance