I can see what your saying Mike. I would counter that as in so many situations there is no perfect answer (well rarely) and it's about the best possible.
I think one thing that is important is clarifying that it isn't just about the balance of the unit and the resultant nose weight, it's also about mass centralisation.
If mass centralisation sounds a bit grand then lessening the pendulum effect or yaw inertia (as Dr Darling calls it).
e.g If the gas cylinder and the battery don't fit on top of the axle we put them nearby and not in the gas locker then balance it with the awning at the other end. At this point we then get into asking should we put the gas cylinder somewhere without easy access?
The more I watch the more bits I don't like about this film:
The two masses. The rear mass is larger and extends further back than the front mass goes forward. I bet this unit had a negative nose weight.
I don't know if it is relevant but there is not one trailer but two in sequence as the car is attached to the table with a bar pivoting at both ends.
Another good piece on stability I found is a PDF that I couldn't get to link elsewhere but appears to work here. [You must be registered and logged in to see this link.]
One of the major factors found in this is the relationship between the distance to the axle from the towball and the entire length of the trailer. This is borne out in practice you can't get a Dart or a Designer to snake and the distance from the tow ball to the axle is two thirds of the total length. A six will snake a Highside Designer certainly will as the tow ball to axle length gets closer to half of the total length.
Look at the film again the axle is only half the total length away from the tow bar.Even the longest caravans don't manage this.
Just found a piece about Dr Darlings report. It isn't the report but is an overview.
Previous work on car-trailer stability has been largely limited to theoretical studies with some reference to practical experience or accident statistics. In this study, extensive and systematic experimental investigations were carried out oil a combined car-adjustable-trailer system. The influence of different trailer parameters on the system high-speed stability was examined by changing the mass, dimensions, and inertial characteristics of a fully adjustable trailer. It was found that the dominant factors affecting stability were the trailer yaw inertia, nose mass (mass distribution), and trailer axle position. The tyre pressure also affects the stability, although this effect is less significant. It is interesting to see that the trailer mass alone does not dramatically affect the high-speed stability, as this runs contrary to current guidelines relating to limits on the relative mass of the car and trailer. Experimental tests on a friction stabilizer and on car electronic stability programs demonstrate that both of these improve the high-speed stability and help to delay the onset of 'snaking'. Author Dr J Darling