[Kevan]

I don't know why you've stipulated a guide depth rule, a guidance size is all that's required, if you decide to enter a car with a deep guide it wont get round some plastic track which is punishment enough.  A piece of Scaley track is all you need to make sure your car won't have problems, there's a straight section sits on the floor next to my workbench and get's used to check my cars every time we're going to drive on plastic track.