I have an 81 and an 82 18 and here is what I was shown to do with dolphin striker tension.
An individual that raced Hobie 18 Worlds told me to just set up everything snug and then raise the mast. This allows the weight of the mast to force the front crossbar down. As a result, the hulls will then be canted outward which is undesirable. You will want to make sure that you have the hulls sitting on something flat and soft. I initially did this with the boat sitting in my driveway on some long strips of carpet under each hull. After raising the mast, we then measured from the top of the bows just under the lip from hull to hull. We then measured the distance between the hull bows approx. 12 to 18 inches lower. After collecting these measurements, we then measured from the center of the rear of the hulls just under the drain plugs at the rear.
Once you have these three measurements you can then determine the amount of cant in the hulls. The three measurements should be the same. As the mast pushes down on the front crossbar this will cause the hulls to cant outward. This will result in a larger distance on the lower front measurement than the top. As you tighten the striker, this will induce more upward bow in the front crossbar and result in less cant. Initially, I had to back the tightness of my striker off. Ironically, this is not going to be a huge adjustment. Once we had mine set, we dropped the mast and the striker actually became loose to the touch
If you really want to get hardcore then try this also. Once you have everything set, take the boat out to the water and ensure that everything is seated correctly (crossbar bolts, crossbars, etc.). Bring the boat back up to shore and check everything again. If all the numbers are equal, then condsider yourself finished with the hulls. Now on to the rudders, but that is for a different post.
Hope all of this helps, and hopefully someone might add to this or even have a better way. In all reality, if you just want to sail, then all you really need to do is snug the striker down until all the play is gone. Then go play.