I've towed my GT a few times now. Not on purpose, mind you, but still . . .
The forks are very solid up front. Get some Soft Ties
to wrap around the forks up high. The Soft Ties will help keep the straps away from the fairing. Do watch for brake lines, obviously. Cinch them down snug, but don't over-tighten. Remember, the DuoLever fork won't compress like a normal telescopic fork will.
On the rear, you can use the passenger foot peg brackets which are very solid. You can also use ties to the passenger grab handles which are up higher, but the foot peg brackets are stronger.
Obviously, a wheel chock helps tremendously, as it keeps the front wheel (and thus the bike) from moving forward, backward, or especially sideways.
More than once I've had to rent a U-Haul truck to get the broken bike home (damn final drives). In one case the truck had a wooden floor so I bought some cheap 2x4's and a hammer from the local hardware store and nailed them in place to keep the tires from moving anywhere. Two long ones alongside both tires, and one short one on top of those in front of the front tire and another short one behind the rear tire. Another truck had an aluminum floor, so I had the 2x4's cut to match the length and width of the truck bed and nailed them to each other in place. That was for a long trip out of some twisty mountain roads but it worked very well.
Obviously you want to pull the straps down as low as possible, but sometimes you gotta work with the truck/trailer that you have.