Chris, I was watching some resto show and they were doing seat cover installs. They used silicone spray before installing the vinyl.
Have you ever used that technique? In the videos I've seen of installs, none had suggested that, but it sounds like a good trick. Not sure if it would react to the leather, though.
Another trick I saw for the headrests was to put a bag over them and apply vacuum to shrink the foam temporarily to slip the covers on.
@SOEBOMB yeah, the website always directs to go to a local installer, but it's not rocket science. Does require some hand strength, I would bet. Post up if you pull the trigger