From what I have read on these boards, a righting pole doesn't install well on a H18 because you can't rivet it to the underside of the front cross bar due to the sloped design of the trampoline (do so and the stern end of the pole drags in the water). One poster, Dan P., made a very slick aluminum bracket and mounted the righting pole on the bottom of his dolphin striker center post (see link). I'm currently torn between a pole like Dan P.'s or making a less expensive homemade "Solo Right" (use the search for more info. on that)......
http://www.hobiecat.com/forums/viewtopic.php?f=15&t=6558&hilit=righting+pole