Hello Dusty,
Bearing in mind what has been discussed earlier about rated loads which are specified and measured statically, and the effect of towing dynamics which will increase the actual loads applied by a considerable margin, responsible manufacturers will specify safe maximum loads, and in every mechanical respect there should be no concerns at operating up to those maximum loads because of the extent of the dynamic load margins they have to cater for.
That does not mean you can be cavalier about exceeding the specifications. The dynamic loads involved are almost all due to accelerative forces which don't mathematically add to the static loads but multiply them. So if you overload the static specification by say 10% then the dynamic loads will also be 10% bigger.
This same concept is applicable to nose loads, axle loads, tyre loads, Maximum permitted towed loads. All these features need to cater for very large dynamic loads compared to their static specifications.
For example, lets consider nose loads, if a tow hitch is rated at static 75kg, dynamically it will be designed to handle at least 3 times that. Consequently it's perfectly safe to leave the caravan coupled to the car when stationary and then enter the caravan to make and eat a meal.
In the case of tyres, we know from previous threads that tyre pressures are quite a contentious issue, but I hope there is general agreement that tyres pressures need to be set to keep the flexion of the tyre wall as the wheel rotates within a particular range. As the tyre rotates when towed the continual flexing of the tyre wall generates heat. This is normal and allowed for by the tyre manufacture.
If a tyre is underinflated this means the sidewall flexes more and will generate excess heat. Excessive heat is detrimental to the tyre compounds and will accelerate failure. But even a properly pressurised caravan tyre will frequently be subject to increased load due to the dynamics of towing, but the important difference is the excess will be momentary, and often followed by an almost equal but opposite underload which means the average heat generation will not be outside its safe range. So again a tyre can easily withstand more than its rated load when stationary or when negotiating a kerb/speed hump at slow speed.
I hope this puts peoples minds at ease.
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