Ya, in full screen mode that might be a problem kind of like flash. Here is a idea if all else fails you could try just making it the same size that it is in its cropped mode but don't make it full screen just use css to style the rest something like:
<style type="text/css">
canvas { margin-top: 0px; }
body { background-color: #F78F1E; }
</style>
Then for your SEO you could just throw in some div tags any place you want, and even write a wall of text 20,000px tall if you wanted to, and then in your styling just do something like this:
#your div name {
text-indent: -9999px;
{
Then all your text will be off the screen, and all the google, yahoo, and bing crawler bots would be able to rank your site. This should keep your site looking the same as it does now. It's just a suggestion though.
Now you got me wanting to make a site with C2 just to see how this would work.
Anyway, I like your site, and good luck with it. <img src="smileys/smiley1.gif" border="0" align="middle" />