OK, here's my system. These photos are from my 14 and 17, but I use the same system on my 16 and also used it on my Tiger.
Here you can see the strap (part #1793 in the Hobie Catalog) and the tiedown (green) as they are for trailering.
This is the tie down - it's just a 2 foot long piece of 1/4" dacron double braid with an eye splice in each end. (Splicing is really easy to do - I did 16 of these sitting in front of the TV watching football one weekend.) The original piece of line was about 4 ft long before the splices were done.
On the 14 and 16, the tiedown loops over the top of the pylon and around the sidebar (look closely in the first photo). On the 17, the eye strap keeps the tiedown from sliding towards the middle of the trampoline.
The strap kit as it comes from Hobie includes plates that get bolted on to the pylon bolts, or pop-riveted to the deck flange on the 17 and 18. You're supposed to hook the ends of the straps into those. I went with a universal system for all my boats that requires no modification of the boat to work.
What you really can't see in the photos is that the rear straps angle forward and the front straps angle aft. The boat can't move backwards, forwards, up or down. In fact, the air resistance of driving down the road actually makes the boat plant itself even better on the trailer.
The only problems I've had with these straps are flutter and when they get wet, they stretch. You just have to keep an eye on them in the rain and tighten as necessary. If they start to flutter, just put a twist in them.