Rich Heimlich wrote:

Now the big question is, 16, 18 or 21 cubic feet? This will likely be
going onto a Chrysler Town & Country LXi so the roof is fairly large
and I like the idea of having more space if needed for future trips.

"More space" to carry what? You've got a lot of products to choose
from; what's the right one? Well, that depends on what you're gonna do,
doesn't it?

Personally, I think that if you need to tack another 21 cubic feet of
space on top of your vehicle (which is probably an SUV, for most people
who choose that option), then maybe you need to be asking yourself some
lifestyle questions. If you're moving across the country, get a moving
van; if you're going to the mountains or the ocean or to grandma's for
the weekend, you won't fill up that box, unless you're filling it with
stuff that you won't end up using.

But I digress. If you're getting it for skis, then your concern is
length, not cubic feet. I got the...jeez, what is it, the space
booster, I think, about the smallest cheapest Yakima box that isn't a
shorty. It's long enough to take my super G skis, and that's all I care
about. Have I ever used the box to transport things other than skis?
Sure, when we were cleaning out my dad's house I threw the box on the
car and used it to carry long stuff like garden tools. My point,
though, is that if you don't have a fairly specific use in mind when you
buy, don't just get something bigger for "other uses". It's
overconsumption and a waste of your money.

As far as putting it on and taking it off goes, my relatively small box
is about a five minute job...but it is a smaller box, and I'm putting it
on a sedan. If you're putting a big box on top of a van, it'll probably
take longer. Also, it's really important to get it on right. You can
put it on and take it off every weekend, if you really want to, but I
don't think it's a great idea. One day you'll be in a hurry, and you
won't tighten things properly, and things will start blowing off on the
highway and going through somebody else's windshield. Or, less
consequentially, you'll scratch the hell out of your nice shiny van as
you horse that box up and down off the rack.