Going on trip, need more luggage space

I don't know your timeline, but a cargo rack should work. Something like this, perhaps.

 

Seriously, I would just rent a van for the week.

 

How big is the dog? Would all concerned be happy with him/her/it in the middle of the back seat?

I've packed enough into our Prius to last the four of us on a month's camping trip: fridge, stove, sleeping bags, tents, etc, etc. There are all kinds of nooks and crannies to fill with stuff, and I'd like to think you could get away with no roof box at all. The best advice I can give you is to take less stuff.

 

Check out Thule and Yakima - both make after market roof racks that fit the Prius. It's a tower system, where they essentially clip onto the sides of the car and you're good to go. I have ones by Saris (pictured at the very bottom of Darell's page linked above), which work great - unfortunately they discontinued their roof rack line.

And as you can see from the pictures on Darell's page, these types of roof racks can hold plenty of weight - 2 70lb kayaks, for one

 

Saris is wonderful. I got mine used off of e-Bay, and they were absolutely worth it. They take a minute to install, and everything was very secure.

 

I have both permanent racks (Yakima Landing Pads) and removable racks (Saris). Although the Saris are not sold by the manufacturer anymore (but they still support them) Yakima uses the Q-Towers for removable and Landing Pad #7s for permanent (Like Darell's). I prefer the landing pads as it only requires one person to install them, do not make a whistling sound, and pads do not affect gas mileage when racks removed. Usually my wife has to help me with the Saris to ensure I do not scratch the paint. I am not sure how easy the Q-towers are.

They both fit the Thule Spirit Box without any other equipment for an additional 16 cu ft of space and a low profile. I chose this box over the Yakima (even though it was $200 more) because it sat lower, was adjustable so I can configure it so that it does not hit my rear hatch when open, had a more aerodynamic look, and was not black (I did not want my stuff to be cooked in there during the summer).

I got all my stuff from the above link. They had very good prices and customer service. I order both on phone and online through them. To get the landing pads installed (if you do not want to do it) look for a bike shop not a car modification shop. The bike shops usually have more experience putting on the racks for bicycle carriers.

BTW, if you order the cargo box from them you have to have it shipped to a UPS distribution center (where you can pick it up) or have it shipped to a business address. The box is huge so usually put on a semi which cannot go into residential areas.

 

<div class='quotetop'>QUOTE(Tadashi @ Nov 27 2006, 01:58 PM) [snapback]354516[/snapback]</div>

How huge is it? I had a 17 foot kayak delivered to a residential address (it just fit inside the normal UPS truck)

 

Well it is smaller than the kayak, but UPS would not take it. The dimension are 90.5in(l) x 32.7in(w) x 14.2in(h). This is about half the width of the car and 3/4 of the length.