When I trailer my I/S, I tie it down like the first picture that was posted. It may be overkill, however, I use 2 inch ratchet tie downs with stainless steel quick links on the ends. I just don`t trust the hooks on the ends of the tie downs. I want something that can`t unhook itself if I hit a pot hole. My wife and I will be at the Dragon`s Tail on May 30 and 31. I`ll watch for another Valk.
If you hook the strap low, you don't need to worry about it coming unhooked..
Hooking low, you have taken all the bounce out of the bike without crushing the front forks.
When I 1st started motor recovery, that was the way I used to hook them in that 1st picture. Almost lost a motor coming down the grapevine just outside of LA. It had bounced up and down on me and worked itself loose. I had a car pass me and tell me about the bike, I pulled over into the emergency park lane and fixed it. From then on, on every recovery we experimented till we come up with the 'Hook em low and go'. Over the years I have hauled several of my bikes across from the left side to the right side, and never had an ounce of trouble hooking this way.
In 1989 or 1990, I got T-Boned right in the middle of the trailer at about 65 MPH. My truck broke loose from the trailer, it went in the ditch and did a couple three, side way wobbles and then slammed a light pole. Broke the pole off it hit so hard. The trailer was almost bent double, but the bike was still rock solid under the conditions. The Trooper who investigated the accident, said he couldn't believe that bike was still on the trailer. The recovery company in PA unloaded the bike, drug the trailer up on the flat bed. Wife drove the truck to the motel and I rode the bike.
So, you fasten them your way and good luck if you are in an accident, especially a 'T'-Bone. My comments above are only for your information.