I always thought of this, about the 5th wheel being behind the pivot of the tandem. I was only like 7 maybe when this first came out and I thought it was 'weird' then. I knew that it would take weight off of the front end, and make it dangerous if the truck had to turn on rain or snow. I've never seen it before except in this, a "Holly Wood" film? I figured the trailer was either empty (for the movie) or that nitromannite was a "light gas" and had hardly any weight??? Who knows. But there are videos on youtube from the show and that is "correct" placement. This is a real "Rubber Duck" truck look-a-like except missing the brush guard, but this thing can take corners like a sports car (with an empty trailer I'm sure).
This is a very cool music video and you can see that the trailer WAS that far back
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Here are some pictures of my Rubber Duck (it's not as 'correct' as MCM Ohana's truck tho!) https://plus.google.com/u/0/photos/112620524923987400441/albums/6145608448363563393
Hope to see that trailer when it's done!