Key point in securing your load properly are as follows:

• Use 4 Anchor Points: Attach two straps pulling forward/outward at the front and two pulling backward/outward at the rear of the front wheels. This of course applies to vehicles such as the Slingshot, Spyder and so on.
  Don’t forget though, as the same applies when strapping down a motorcycle. You want attach two straps pulling forward/outward at the front (lower triple clamp or frame for example) and two pulling backward/outward at the rear (passenger peg mounts or subframe)

• Use Soft Loops: Route soft webbing loops around frame components rather than hooking metal strap ends directly onto the bike to avoid scratching paint and chrome.