Magnific Popup — setting width and height of iframes

Ok, I was able to implement the avia.js edit solution for including external website iframes in the new lightbox feature for Enfold 2.9. However, the old simple way of setting the height and width of the lightbox in the old PrettyPhoto plugin has also changed. Is there a way to bring this feature back? Looking around, it might require setting a hard class attribute, but that is far from ideal.

Also, if an image with lightbox selection is large enough to come underneath a nav dropdown, it will interfere with the dropdown, preventing the user from accessing it. Is there a z-index that must perhaps be changed to prevent this interference?