OK, I think this just doesn't work for spidertrons. When I place down a car or a tank - then "created surface ..." debug message appears. That does not happen for spidertrons.
Pity, a spidertron is a perfect place to put shopping mall into.
If you are going to fix this particular problem, then may be fixing the player positioning would be a nice idea, too. If you enter a car by mistake then it's really annoying to run all that distance just to exit it.
