Hi @gary.
Nice. You could avoid that jump (with the image load), by stacking the images rather than replacing them. Then on hover you adjust the opacity. All that can be done in the class editor.
You could then add a transition style in some CSS to add fades etc. (that would be the only bit you need to add to the page header).
Quick example… something like this (few ways you can do it).
Example_Image_Swap_On_Hover.bloc (1.5 MB)