Hi Jim - I started on a P16, very similar to your P18. I now have an I20, which comes stock with the jib battens parallel to the forestay (about a 45 deg. angle to the leech). They roll up into a very small cylinder, which is how we store the boat (with a protective jib snorkel-cover). This way works well for us, and I suggest you try it. The leech hollow method also sounds interesting.
Sail fast and have fun,
Alan Thompson
I20 - San Diego