I tow a caravan with a 903cc 4 cylinder engine and the thing is rock steady at 70 mph in most winds except gales. Mind you and kind of wind (especially croswinds) slow me down and inclines of course. The onely thing I have worried about is braking hevily in th rain. I have no van brakes because it is only 200Kg (ish) and the car is about 600Kg but even so the extra weigh behind drive the car under deceleration. I usually take two or thre junctions to get the mindset needed for the extra stopping distance in the dry. I once had to swerve to miss a badger who was big enough, I did not avoid him and with all the swerves and bucking and then both the car and the van bumping over him it was quite an experience. Basically any sudden move is fraught.
The usual advice is think ahead - because the other idiots won't. They will put you in situations. And don't go down any narrow roads unless you know there is an exit or a turning place. I can unhitch and move the van easily but I have yet to risk that on any real slope, even at 5 mph 200Kg can do a lot of damge and on a campsite that is no joke. I made a spiky thing for the jockey wheel to sit in and dig into the ground - for that very reason. You never know if I might be in the van when it started rolling - embarrassing or what!!!

Oh yes and --- enjoy.