If you've been sucked into ticking the four key option box, that gives you keys you'll never use. I think someone has already suggested that you can take one of those keys to pieces, extract the blade, and use that as Surfer key. That way you also have the electronic box as a spare should you need it.
I previously wrapped up Surfer key with insulating tape, and then fixed it to the wiring loom. That way I think you'll be hard pressed to have someone being able to find it. One tip is not to secure it too much, or in too difficult a place to get at, that when you want to retrieve it in the middle of the night, you can't.