I bought a Thule cargo box this spring when they want on sale, the "Large" size (16 cubic feet). That alone was expensive enough, but I could not stomach handing over $250+ for the Mopar or Thule brackets and cross rails.
Besides the cost itself, as we have seen in other people's photos they sit comically high on the roof (not something I need since I don't have the sunroof), and the brackets wrap over and totally wreck the good looking roof line on the rails. They also just plain don't look very sturdy, IMHO.
I decided to go my own way. Grabbed some scrap angle iron from an old bed frame, a spare piece of 3/4" metal conduit, and a handful of bolts and I was on my way. Cut four pieces of the angle iron, measured and drilled them out with my cheapie drill press. Chopped up the conduit and bored some holes in those, and I was pretty much done.
I was in a hurry to go camping so I only had time to paint the brackets, which was the important part since those are intended to be permanently affixed to the inside of the rails.
The conduit crossrails I will be pulling off to clean up and paint. I was thinking of just putting black foam pipe insulation over them and 3D printing some caps for the ends. Thats all in the aesthetics department, but we went hundreds of miles with our tent and my golf clubs up in the cargo box and it worked great.
These are the brackets I made just before installing them:
A couple of quick videos:
The Thule box has four claws that can grab onto just about any shape. I could have cut and bolted a couple of 2x4s with black indoor/outdoor carpet stapled to them and it probably would have worked just as well, but the metal tube seemed less obtrusive. I don't intend to leave the tubing up there when the cargo box is not in use.
Thoughts and things I would do different:
The angle iron works great, but I wish I would have used better paint and had more time for it to harden up. Actually was thinking dipping them in a bedliner or something durable would be the best route. I wish I would have welded the 5/8" nuts on the bottom of the brackets, it would have made putting the cross rails on and off easier and less potential to scratch the roof fumbling around, definitely lay down some cloth to protect the roof.
I used stainless steel 1/4" bolts and blue locktite so other than touching up the paint I don't plan to take these off unless I need to, but if I did I'd weld the nuts on and paint them better or coat with bedliner.
The brackets are the most important part. Literally anything can be a cross rail now. If I was hundreds of miles from home and really needed it, a couple pieces of board would do so long as you had access to a saw, drill, and some bolts.
I had hoped to do something different to try to put the weight more on the factory rail itself, rather than on the brackets and bolts, and I may eventually get to that but I have not put anything heavy enough on top yet to worry about it. Feels super solid when you grab ahold of one of the bars.
Initial thoughts on the Thule cargo box: The "Large" size is pretty darn huge. Its really nice in terms of added storage, but to get it far enough backwards to be sitting decent on the roof you have to unscrew the AM/FM antenna, and it has tremendous drag
on the 65-75 MPH highway. My gas mileage has taken an enormous hit, as low as 22 MPG on some short trips driving into the wind, 24 MPG on a 65 MPH highway in a rainstorm, really struggling to get 26-28 MPG on fair weather days. The box is aerodynamic but you can still hear the air rushing around it, about as loud as having a window cracked maybe, so not totally objectionable or loud but you won't forget that its there.
The worst part is that its the straw that breaks the camel's back for the transmission. I don't know about everyone else's car but despite having the longest legs (final drive ratio), mine loves to get into 8th gear on the highway, it always has the first 28k miles of owning it, and yet as you know it takes very little in terms of a hill or an incline and it has to drop to 7th. Well, add one large cargo box to the roof and now its dropping to 7th all the time, and I mean ALL the time, for the slightest hill or gust of wind. Its bad enough that it will eventually give up and hold 7th on its own, something I've only previously seen when towing a washer, dryer, and standing freezer that was up in the wind. Knowing this, I now slap it in manual mode as soon as I get to highway speed to force 7th just to avoid the first 10 downshifts before it catches on. On a windy day, dropping to 6th is slightly better (mileage-wise).
I had expected some extra drag and mileage loss but its so extreme, it just emphasizes how close the engineers shaved it when they ran all the numbers and figured out engine power and gear ratios. Adding this cargo box threw it all out of whack and in two tanks of gas it has not seemed to adjust to it either. So, its nice to have but I won't be leaving the box up there when I'm not using it, because I don't like having to use manual shifting just to go to work and back without the transmission shifting 64 times.
I bought the largest box I could get. All I really needed was enough length for downhill skiis, so to anyone else looking at something similar I would say don't over-buy because I'm looking at $50 more in gas to go to the mountains with the box on vs box off, and I probably didn't really need 16 cubic feet. Of course at slow speeds the drag is negligible so if you only drive around the city and don't go miles and miles on a 4 lane highway every day for work won't be so bad.
That my 2 cents.