I took a look at your suggested location, and I was a bit concerned that the strap would rub on the paint.
With no other ideas coming to mind, I decided to consult the experts. I emailed Honda's customer support. They responded with a PDF copy of the owner's manual, and they directed me to page 154 for "helpful tips on how to appropriately transport your scooter." Duh, maybe I should have looked there first! However, here is the full text of the "helpful tips:"
If your scooter needs to be transported, it
should be carried on a motorcycle trailer,
or a truck or trailer with a flatbed area. Do
not tow your scooter, as towing can
seriously damage the transmission.
When contacting a towing or transporting
service, be sure to ask if they have a
flatbed area, a loading ramp or power
ramp to safely lift the scooter, and
motorcycle tie-down straps.
The email also contained a phone number for customer support, so I decided to give that a try, no matter how long I would have to wait on hold. It turns out that I didn't need to wait on hold for long at all. A friendly dude picked up the phone, and we chatted for a while. He ultimately suggested (but the lawyers wouldn't let him recommend) hooking straps onto the bottom triple clamp, which would let me get some compression into the fork so the scooter wouldn't bounce around.
The triple clamp doesn't seem to have any holes machined or cast into it, so I ended up wrapping some strap loops intended for handlebars around it, and then running straps from those to the tie-down loops in the truck. All in all, it worked pretty well. Only a couple of minor drawbacks to fix:
1. Because of the width of the tie-down loops in the truck, the straps came dangerously close to the side of the fairing, and I was worried about marring the paint.
2. With the forks compressed a bit, he front fender extends past the front edge of the tire, so I had to put some spacer blocks in front of the tire to keep the fender from scraping the bed of the truck.
One thing I did to aid loading was to use straps on the luggage rack, lightly, to keep the scooter upright while I messed with the front straps. I kept those in place for the ride, too, just in case something went wrong with the front straps.