I think it's about time people stopped giving false assurance that if you abide by a NON OFFICIAL GUIDE LINE of 85% of the kerdside weight of a tow car, you are guarantee'd some sort of safe tow situation.
I can see HGV Dave's point and yes he is jesting.
I once refused to bring a spud bulk load back because it was 6 ton over weight for my 4 leg tractor unit. The boss went ape! But when I pointed out that the 6 legger had been sent to a job that mine could of done, it transpired that the driver of that one had persuaded the transport manager to let him go to Scotland on a 3 day jolly to fetch just a 14 ton load.
I've been tugged by the law for towing a trailer that "looked too big" for my car, a few years back. I was towing a 16ft beavertail trailer (single axle) made from a caravan chassis, that was loaded with 65 empty wooden box pallets 5ft long 1 1/2 ft wide and 9" deep. The load and trailer weighed 1100kgs and was about 8ft tall. I was towing this with my Renault 18 GTL estate (1647cc), with the full knowledge and approval of west midlands police. You see, they had stopped me towing it with our VW LT35 curtain sider as it hadn't got a tachograph fitted. (thats another escapade). They even stopped the traffic so that i could take a run up to get back onto the highway from where they had impounded the LT35. This trailer looked absolutely stupid behing the car, but it was legal ??!! My dad who'd had to drive my car 50 miles to meet me was absolutely dumfounded that they couldn't allow the truck to tow the trailer home, but they would allow the trailer behind the car. He even refused to drive the car and trailer. So I had to drive that and he drove the truck. Of cause, when I got stopped at Droitwich for having the trailer behind the car, my dad blew a gasket at the copper and nearly got booked for verbal assault.
I agree it would be a hell of a task to test drive every car and caravan combo. PC already has a good loading guide to help folks load the van correctly. There is a simple way of measuring the hitch weight which we all have seen before.
The best thing PC could do would be, to do a feature on where the VIN plates are on cars and how to read them correctly.
That in it's self would promote a good towing mindset. It would also be using the data that the police and vosa use, which would reduce the confusion when caravan outfit's are spot checked. People all too often refer to the handbook for their car, which usually covers all models and engine sizes in one generic book, and then can't understand why the VIN plate figures are not adding up to the info in the handbook.