Grid Layout for Masonry (fixed height)

Hi Tom,

I think I have said it before, but this theme is freaking amazing! I can't believe how feature-rich it is for being as reasonably priced as it is. Thank you for building such a great resource!

I am looking to set my posts page in masonry mode, with one big post at the top, and then posts under it at a fixed height, like a grid. I did some searching on the forums, and in this post https://generatepress.com/forums/topic/masonry-posts-same-height/#post-98274 it looks like you said that you added that functionality right in the customizer. Unfortunately, I can't seem to find it anywhere. Could you please help direct me? Or, if that feature has been discontinued, would you be able to guide me on what css I need to insert to set the height for my smaller gridded posts?

Thanks in advance for your help! :)