Nice buggy, and you're right, I love driving this buggy indoor on clay.
There is a switch mount on the integrated mud guard/radio tray. Be careful with your swith position. I can't tell if where the "on" position is, but it looks like you might have a buggy that will accidently turn off on a hard landing. I like my switches facing side-to-side or with the "on" position towards the front or towards the bottom so it is unlikely to turn off.
Sef can you show me a picture of where the switch should mount? That's the last thing I have to do....lol