perhaps it should be a button on the website, like "experience the site with FCC's Slow Lane".
That way, they can see what the site is like and if they choose to press the button, they can see what it is like to be on the slow lane. Otherwise, the first time visitor may not give the site a chance at all.
If it's a site you visit regularly, it's likely to make you really curious, right?
We're making a version that's just an anigif that people can embed. That should be live really soon. So, that works for people who don't want to interrupt visitors with a message.
That way, they can see what the site is like and if they choose to press the button, they can see what it is like to be on the slow lane. Otherwise, the first time visitor may not give the site a chance at all.