This is how we tied my ST to bring her home.
I worried a bit about the handle bars, but the previous owner, who helped me to tie it, told me he did it many times, with different ST over the years.
I used heavy duty ratchet straps. We made a turn and half around each handle bars, on the inside side of the master cylinders. We were cautious not to squeeze the hoses. We also put a folded rag, between the fairing and the ratchet strap. It worked.
The only place were it left a mark, was on the rear. On the rubber of the rear handle. We probably overtight those knots, or we ratcheted those straps a bit too much.
Note the cable around the rear wheel, to prevent the bike from moving forward.
I drove on high way, for two hours and half, without any problems. Of course, I made a few stops to make sure everything was still tight enough, but not too much. We compress the suspension a bit, at maybe two third, so it was still able to work a bit, not much. All the suspension work was to be made by the trailer and the towing vehicule.
I'm not saying it's the best method. But it worked for me.