Yes, I know. Virtually every lego car builder eventually builds the tumbler and the BTTF Delorean (coming soon). Here is my attempt at it. I don't have a lot of parts (especially tiles) so I had to make the best of what I had for greebling. 29 studs long x 16 studs wide x 10 studs tall. The pop can is for scale reference.
It has "hand of god" steering. I know this is not how the "real" tumbler's steering works but it is strong and allows my son to drive around the room. If you can figure out how to make more accurate steering (at this scale) let me know.
This is very accurate and you've got the shape spot on. I like the studded look and your steering system looks great. I've made a version with steering and it is very fiddly and hard to get any strength. I can imagine it would be nigh on impossible at this scale and your solution seems perfect, especially for little hands.