I bought the Mustang one with a pocket on it. I'm assuming the Triumph one is held down by the instrument cluster bolts, as is the mustang, so it's plenty secure with three bolts and the panel clamping it down.
The strings in the rear to lace it down are probably intended to go around the rear tank hinge/mount, to hold the rear portion taut. On the Mustang, there's a thick elastic band there that does that same job.
The Triumph one should be no harder to install. If it has strings in the front, also, I'm sure it will become pretty apparent where Triumph thinks you should tie those.