Is it possible to insert vehicles into tunnels?
 

I have not been successful thus far. . . Is it possible?

its not possible to change the z value of vehicles im afraid. well apart from the helo but it will explode if its placed in or on another buiding.

the destroyed stuff i reckon will work

and i think the zodiac works in the tunnels:D

I tried the zodiak as well as the pickup. Both reacted the same by appearing on top of the terrain with the tunnel just below it. If you can find a way to make the zodiak work in a tunnel, please share the info. This was to be a major shortcut (hidden of course) in my mission.

Well, I tried to do it too by making a small map. It accepts z values of positive type, but the negative type, it just won't work. Sorry dude, we tried.

Thanks for the help and for trying, guys.