Featured Header image not served from Jetpack CDN

Hi there, Clean Box is a great customisable theme. I also use WordPress JetPack with Site Accelerator (formerly Photon) turned on. I've noticed however that the Featured Header Image is not served from the JetPack CDN, which also means it isn't automatically rendered as a WebP for compatible clients. Adjusting the theme to have it render from JetPack CDN if turned on would be really helpful for improving site performance. Site in question is: http://www.givemesomespice.com I've found a couple of helpful blog posts: * https://eric.blog/2016/11/13/how-to-use-jetpack-photon-for-wordpress-header-image/ * https://allankiezel.com/how-to-fix-jetpack-site-accelerator-not-serving-background-images-over-cdn/ However, my PHP experience isn't up to identifying the right way to do this. Thanks,