Hello Kevin,
Regardless of the actual weight ratio, the driver of an outfit must accept that extra care is needed when towing any type of trailer. Caravans present thier own charateristic hazards. They tend to be large for their weight and thus can very easiliy be affected by side winds and the bow waves from other vehicles. each outfit will react differently to these conditions, so it is difficult to cast-iron advice.
However, it is generally accepted that the heavier the tow vehicle in relation to the caravan the less the caravan will upset the tug. That is where the 85% guideline comes from. But this is not the whole story, there are many other factors that will contribute to the towing experience, weight distribution in the van, tyre pressures and the drivers ability to have empathy with the outfit and road conditions.
By towing a caravan you will be adding a substantial additional mass that the engine has to haul around, you will experience a loss of perfomance, so you must allow more time and space when driving. do not expect the outfit to be as agile as the solo car, think of it more like a bus.
Taken with care and assuming your outfit complies with the road vehicle regulations, you may find you have no problem with 92%. Of course you do not have to load the caravan to its maximum weight so you may be able to closer to the recommendation of 85%
Go carefully and enjoy