You did a good and clean job, for sure your tutorial will be useful for actual or future 5571 owners. They're even warned that thoses damn 18 patern tiles are really hard to find
In 2005, there was no LEGO official software, parts files were in .dat (and some were really difficult to find), and I didn't know at that time if making instructions was possible. So the only thing I could transmit was the first .mpd file (I still have it).
For weight problems, I think I was more concentrated on looking for solutions for other conception problems, the (mono) pneumatic system for example was a great occupation. The other problem with that kind of structure is that when you conceive a 3D model before buying anything, you know it will be virtualy huge but didn't how exactly, so I made a (maybe too much) basic thing for the wheels, and crossed my fingers. On my first pictures you can see that the 2 back end wheels suffers a little. The fact I wanted the trailer to be slighlty (and intentionally) slopped doesn't helped for sure. Globaly, it was important for me to refer to something simple and classical like that.
Maybe a 16 axle tense with many technic bricks (wholes) could be a improvement ?
For the rest (doors problem), as the first model was modified by someone else, I can't assume what happened after. The only thing I remember is that the solution I found was the best at that time and worked great. Your solution seems to look like mine.
If I can notice two missing things : the red tiles to complete the red roof line, and the black cat on the front (which is the perfect link between the truck and his trailer )