The 85% is only a recommendation, and its origins are shrouded in mystery, but it does represent a reasonable area for the towing ratio. But don't worry if your a couple of percent different - its not a legal requirement.
The most important thing is have an outfit that you can control safely:-
Look up the guidance on how to load your caravan to maximise stability.
Make sure your car and caravan are mechanically in good condition, especially check suspension and tyres.
You will need more time and a longer distance to pull out into traffic.
Give plenty of clearance to other vehicles and road users ,
And most of all remember there are lower speed limits when you are towing, and the limits are limits not targets.
Instability is always worse the faster you go, so if you do encounter the onset of any instability - slow down.