I'd like to offer you congratulations, and many miles of happy sailing.
You and I have the same H18SX.... 1989 Nationals Boat, with some modifications.
I too, paid a good deal of money to Chip, and I am very happy with his work. Later, we added a 5:1 downhaul, mainsheet overboard preventer, (really just a piece of shade cloth between the two tramp halves), Robbline main and jib sheets, EPO rudders, FX4 hiking stick, and last year, a Tiger spin set up. This past winter, I refurbished the furler, now runs smooth as silk. With some indoor/outdoor carpeting and some epoxy, I added 'protection' to the inside corners of the dagger wells. Hobie used to sell a neoprene kit for just that purpose... it is critical so you can maintain 'good' edges on your daggers. email me off line for details if you want.
Coming from H16's, you've probably been told to remember to 'raise' the daggers when running in shallow waters.... I have many stories. Lucky I had a spare set of daggers.
When running downwind, you will be AMAZED at how much buoyancy there is in the front of the hulls. Last Weds evening, during club racing, my son and were running under spin in 10 knots when we were hit with a 20 kt gust.... we took water up to the front cross bar and of course the boat slowed way down for a second or two until it could come back on an even keel. Other than that.... no problem.
I recommend you find a quiet spot, and with some helpers, capsize and right the boat under controlled conditions. So when you do end up going for a swim, you know what to do with comfort and ease.
1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'