Some updates to hold you guys over:
I got a tracking number from Koolance. The proper res will be here on Monday (I hate cross-country ground shipping). I did like the dual bay res while I had it in my hands. A few things put me off, though. 1, the volute didn't appear as good as on the 401X2 from the pictures I've seen; 2, fill ports on the side of the res, not the top like on the 401X2, which would make filling a PITA; 3, it wasn't what I had ordered. A good quality piece, no doubt. I would recommend it if someone asked me about dual bay reservoirs.
The mounting bracket/system for my external radiator is nearing completion. I spent 2 days with a dremel cutting away at 1/8" steel (it might even be stainless) to get it how I like it. I had to make some changes to the original design because I realized that the original design made it impossible to run fans on both sides. Current design allows for up to 38mm fans between the case and radiator. Although 38mm fans would fit, they would likely be almost right up against the side of the case. I plan on only running 25mm fans in push for the time being. More pics will be up tomorrow after final sanding and paint.
Radiator next to Dremel in vice for sanding, this is to show the pattern for the mounting holes
Lining up holes on bracket to radiator
Temporary mounting of radiator on bracket, even with only 2 screws hand-tight it feels secure
Approximate mounting location and method of radiator on case
All cuts were done freehand, which is quite impressive seeing as how straight they are. I put the dremel in a vice to sand the edges down. This gave me a greater amount of control than if I had been holding the dremel instead. The tabs you see at the top and bottom are for mounting the 1.5" risers (from McMaster Carr) that will be used to secure it to the side of the case. They weren't part of the original design and the risers were originally going to be mounted in line with the holes to secure the radiator, which would have prevented the use of fans on that side of the rad. Added those tabs so the risers wouldn't interfere with any potential future upgrades.