I'll probably scale up the design to fit the 5.25 bay on the front. Do you want it sideways in the front (as in 90 degree mount and to the left or right of radiator) or above radiator or below etc? maybe mspaint it onto my sketchup.
Also I am thinking that the back panel for the lower chamber would be removable but the others (Front,Left,Right) are glued in.
The question I have is how hard it will be to get to the HDDs. The easy way out is to velcro them all together in the bottom I guess. Hard way is to either make or buy or salvage a cage and throw it in next to the power supply. I am sure if I scale the design up 2-3" cubed there will be plenty of space. You could do 2 of these
http://www.amazon.com/dp/B0034XRDV4/?tag=tec06d-20 side by side. Not sure the best way to retain them in. I have one of those cages, I could measure and mock it up in sketchup. I am just not sure how to mount it in such a way that you can easily remove it.
The easiest way is get some velcro tape and tape them all together in a stack then tape that to the floor of the case.
I also wonder how to mount an externally accessible 5.25 and make it look good. Obvious way is to just make a cut out but you have to have steady hands with a jigsaw to make the square cut out hole look nice and even. Of course a scroll saw would be nice.