I can now claim to have sailed all 3 of those boats (F18(HT), the TheMightyHobie18 and Tornado) since I crewed on an F18HT in the nationals two weeks ago in FL. In the short time I actually helmed the HT, I can say the helm felt quite neutral (heavy air day) and the boat was responsive. While under spinnaker, it was a little twitchy. Can't say it felt much different to the Tornado w. main only. A surprise 'cause I thought the T would be more off balance since the mast placement with regrade to centerboard placement was designed with the jib in mind.

I've singlehanded the TheMightyHobie18 & Tornado many times and sailed both with just the jib a few times in strong blows. Dropping the main is always straightforward...just payout some traveller and turn rudder to weather, effectively stopping the boat ("heave-to" mode), secure the tiller under a foot strap or otherwise to hold the boat in the same position while you go to the mast and drop the sail. Usually is helps to bring the sail down slowly, rolling it as it comes out of the track...this stops it blowing overboard before it's all the way off the mast. Then I just stuff the rolled sail under the footstraps and off I go wit the jib alone. Now usually if there enough wind to make me drop the main, my first thought it to head in an call it a day after getting the main down. On occasion I have re-hoisted the main and continued sailing as normal if condtions change. Re-hoisting is just the reverse of dropping, except there will be less wind (if not...why are you putting the sail back up??).