Special Thanks to mr_ed for inspiring me to finally put that welder to some use.
I finally got around to putting together my racks. These were inspired from mr_ed's thread about his ammo can racks:
Let me start by saying that I suck at welding. These racks are the only the second thing I have welded together. This thread isn't about a finely crafted professional product, but rather the bumblings of an amateur. The racks are welded together by a $69.99 harbor freight parking lot sale flux-wire welder that produces a hell of a lot of spatter.
I was leaning towards going with the ammo cans to stay cheap, but the weight and the potential for damage to cars when lane-splitting made me go with the e21 cases.
Metal used: 3/4" x 1/8" x 6' angle irons (x2) and 1 1"x 1/8" x 4' flat bar. This was enough for the entire rack at a cost of about $25. I also purchased the sw-motech to givi adapter kit. This kit is normally used to allow givi cases to mount to motech racks. The kit was $20. The cases were about $180 with tax.
Using the dimensions of the pl532 cases, I began with forming the rectangular portion of the rack that the cases would mount to. The rectangles are approximately 12x8.25".
After using photos of the actual cases and racks, I determined my height and angle of the rack on the exhaust side first. Using a piece of angle iron to mount the rectangle to the passenger footrest, I then created the mounting tabs that bolt below the rear rack and tacked the rack together.
I created a mount for the license plate bracket out of flat bar and tied that into the rear of the exhaust side. Once that was done, I matched the other side's angle and height.
I found it interesting trying to create something symmetrical on a bike that is not. I went for trying to get close to being even, without having the left side sitting way out in space. I'm pretty pleased with the results.
After tacking everything together, I removed the whole works and welded it for strength. I tried to cleanup the welds the best I could, but the cheap flux wire produces a lot a spatter. I painted it with rust-oleum hammered texture paint to help mask the ugliness.
One day, if I ever get better at welding, I may give it another go, but for the total time invested (about 15 hours!) I'm pretty satisfied with how it turned out. The racks are fully functional, the cases can detach exactly like the real thing. Overall, if you include the cost of the welder, the money spent is a wash, but this way I have the tools to create some more stuff in the future.