One thing to keep in mind with the Harken Hoister is to "balance" the load with the Hoister's weight rating. While it is obvious you don't want to use an 80 pound rated Hoister on a 160 pound roof tent. What is not so obvious is that you probably don't want to use a 200 pound rated Hoister for a 100 pound roof tent. It will work, but just not as well as a lighter rated one. The reason for a higher rating is that there are more wraps and pulleys to give you more mechanical advantage but the downside is more friction. Harken's quality may seem like overkill, with ball bearing pulleys and all but it does make their systems work well. Harken also comes from a marine background and they build in a very high safety factor into their products.
Another nice thing is that if you have a high ceiling, Harken can make you a Hoister with longer lines. I've had them make me one for a 12 foot ceiling in the past. It is special order, but they are a very responsive company to work with.
An observation regarding the garage door height question. Sometimes you can drive your rig under the bar even though the measured height will not allow it. Let me explain, a friend had a garage where we measured his Jeep and his Maggiolina at the highest point. It was two to three inches too high to fit. We still had two to three inches clearance without having to air down the tires. This is because most driveways are sloped up to the garage so your rear wheels are lower when you drive in. Your vehicle will describe an arc and the height at the center of the vehicle is effectively lower. Of course, if your driveway approach is down, this same principle will work against you.
