Hi sailscycle, maybe someone on the Hobie 18 forum could offer a suggestion viewforum.php?f=13
if you have not tried there already.
Otherwise here is a thread that might help spark some ideas: viewtopic.php?f=14&t=42851
and here viewtopic.php?f=23&t=35775&p=149276&hilit=ramp+shore#p149276
and using the forum's excellent search feature you might discover more threads.
Just envisioning... one of those trailer winches fixed to a stake onshore (or to a car) and a less steep and wider ramp might do the trick. Interesting engineering problem to solve. The cat trax method seems ripe with peril but might be worth a try - I just do not have experience with them to say.
Let us know how you work it out!