I have the Shasta which is 48" * 56" closed. I have the extended pioneer series (if I remember right the summit was thicker material and a few other goodies I didn't need for the extra cost). It fits awesome on the gobi rack especially if you have removable cross bars. There's no wiggle room to get your hands under the tent once its loaded so I would highly advise mounting your crossbars first then putting the tent on the rack. For me, it goes right up against the back of the sunroof so I am still able to use the sunroof portion for mounting totes or whatever. On the bottom of page 2 of my
flickr album there are a few pictures of the tent and a video of how I load it. The width is a non issue, it hangs off the rack a little on each side but not over the side of the car. The extra weight you will notice. the drop in MPG is pretty big too. I went camping near Nebraska this past weekend, I had the car loaded to the gills with 4 people, dog and lots of camping gear. My MPGs were hovering around 12.
Definitely watch some YouTube videos on how to set your tent up. I was being too manly and refused to watch them before my first trip so I didn't know what a lot of the 'extra' parts were for. The instructions that come with the tent were kind of useless to be honest. Mine came with extra annex c-channel, a bar for support, the spring rods and other parts. Once I watched a few videos CVT has it all made sense. Another thing to be careful of, zipping the cover up and getting it caught on the tent. I have done this more than once and its a huge pain to undo. Take your time zipping the cover up and make sure the tent is not in the way. They say not to put the annex under the cover but I have done this many times and its no problems. I just spread the floor and annex out evenly over the tent and cover it all up to save room. If you have a lifted 4Runner you may need to order an extra ladder (some come with the telescoping one already). The original ladder on mine wasn't tall enough so I ordered a new one. 8' telescoping should be enough. If you get an annex, buy new stakes. the ones that come with it are weak. I've bent most of them already, and recently bought new thicker ones.