Yeah, the image changed I believe in '81, well after the switch and before the first VHS version in 82. If you do a google search, there is a website that talks about the history of the Fox Logo. Here it is
As for your site, Mike..that R2 CGI stuff is amazing. If you did that yourself, I am VERY VERY impressed. If only you would do a CGI Vader, the possibility for deleted scenes would be endless. Plus, you'd be able to make Vader do whatever he wants.