I completed my rack a few weeks ago, so I guess I should add some pictures just in case it can help someone in the same way that all the other pictures on this thread helped me.
I had never welded before, so I decided to TIG the thing together because I like making life difficult on myself. In all reality, I found using a TIG machine to be close enough to soldering that I took it up fairly easily with my electrical background. I wanted to make something close to a Gobi rack without paying way more than I wanted to pay, so I designed it to be easier to build, but still with a similar look and function.
I chose 1" square bar with 0.065" walls, expanded metal floor, and some inexpensive bar stock (that turned out being way overkill) for the mounting brackets, and finished dimensions of around 4'x6'.
Bottom welded together, mocked up on the (too crowded) garage floor:
P1000541 by
Shaun Rasmussen, on Flickr
Up on the roof to tack on the mounting brackets. I did this before I got the top welded on so that I could minimize the weight I had to wrestle around.
P1000545 by
Shaun Rasmussen, on Flickr
I used the stock rack's mounting points, and tried to copy the mounting methods of a Gobi mounting tutorial that I found. I decided that it seems to work for them, so why try to reinvent the wheel?
P1000547 by
Shaun Rasmussen, on Flickr
Mounting brackets tacked into place:
P1000549 by
Shaun Rasmussen, on Flickr
Completed on the floor after painting it. I used Rustoleum professional paint and primer (I think that's what it was called). I used a roller to avoid the waste that spraying the expanded metal would cause.
P1000554 by
Shaun Rasmussen, on Flickr
Completed rack up and mounted:
P1000571 by
Shaun Rasmussen, on Flickr
Side view:
P1000563 by
Shaun Rasmussen, on Flickr
Overall, I'm happy with the result. With anything that I build, I would have done a few things better/differently if I were to do it over again, but not bad enough to think about starting over again. I think I have a little over $300 into it, and it weighs in at a hefty 75-ish lbs. It is loud on the freeway, so I'm currently working on trying to figure out a wind deflector for it. I have a carbon deflector in planning stages (since I have some carbon laying around). Thanks everyone on here who has posted their racks, it is a great place to get ideas and motivation to build one for myself.