Positioning the mouse hover image at center of the page.

Hello,

I am having issue centering the mouse hover image at the center of a page. I am able to center it horizontally but unable to center it vertically.  Please help me.

Here is the url: https://walrus-sparrow-632s.squarespace.com/portfolio
password: perry

Hovering over to any row will display the image.
 

Thank you!

Removing dynamic inline style with javascript and add a custom css fix this issue.