To all of you concerned about the dynamics of towing a caravan with a rear mounted bike rack,I have just returned from the peak district,a 160 mile round trip with my wife's electric bike mounted on the rack.It did not affect the towing characteristics at all and for me it's the way forward for carrying bikes.
I think you have to take the whole outfit into account.
I've dabbled with weights and load configuration a while back using a Millennco Nose Gauge and weighing absolutely every single not nailed down item in the caravan on digital bathroom scales.
You would be amazed the difference only a few kg placement within the caravan makes to the nose weight.
But then towing speed can mitigate a badly balanced outfit, for example we have moved our caravan twice whilst living in it full time. The bikes and full size steel awning goes in/on my car, then literally everything else is just chucked in the caravan, the inside looks like its been in an accident!
I kept my speed to 40 mph driving once from Truro to Liskeard with a rock solid outfit, which was completely overloaded, with a high centre of gravity and a nose weight of who knows what, my experienced guess 40kg or lesser, as we have the transverse bed void full of vac packed clothes even before we slung a load of coats on the bed and the above lockers stuffed again with more clothes!