[totaltec]

Phil,
The only thing I see that I don't understand is the abstract declaration.
It also looks like you are missing defining {} brackets around your class itself.

abstract class Converter extends \XLite\Core\Converter implements \XLite\Base\IDecorator
{
Function goes here
}

Other obvious questions are, is this module activated? is it functioning in other ways?

So, I investigated this and was able to successfully change .html to .htm

But when I tried to change it to / it failed 404 error not found. So I think some .htaccess magic is needed in addition to this change.