3/6 2.5" to 3.5" bay?

There are any number of 4 2.5" disks to 2 3.5" bay converters. These are, simply put, made for the past when 12.5" disks had any significance. Today you either want a 15mm high 2.5" disk for mass storage (5TB ATM) or you want 7mm high SSDs. So... is there a thingie which allows mounting 3 thick HDDs or 6 SSDs in two 3.5" bays?

Some clever engineering would allow 7 SSDs because that's only 49mm vs the 50.8 of the two bays but that's perhaps too much to ask for

I could imagine some plastic rails you need to screw to the side of the disks and then you just slide them into the bay and let gravity handle the rest for the SSDs. Sure, the HDDs would require screws but the SSDs do not really need much.

If such a thing does exist, I can think of several potential issues that would come along with fitting so many drives in such a small space. For one, some SSDs can heat up quite a bit with sustained used, and in such tight quarters it wouldn't really have anywhere to go unless the drive caddy in question doubled as a high performance heat sink, at which point you're probably getting into new case costs. Second, just imagine what it would be like hooking up 7 sets of SATA power and data cables in a 50mm space. I'm thinking cable management would be a deeply unpleasant experience.

That said, what exactly are you wanting to do? Is there a certain number of new drives you're trying to fit into an existing case? If you've got a spare 5.25" bay, there are adapters that will let you mount up to 4 SSDs (just search "4 ssd to 5.25 bay" on Amazon). If you're needing to add a substantial amount or hardware and you're just really starting to run out of mounting options though, it may be best to start shopping for a new case that's better designed for what you're trying to do.

I am trying to design a case Are you perhaps interested in a 177mm high (yes, 4U but it's much smaller than a rack case), 20L case which fits an ATX motherboard and 11.4" video cards? (only SLI, triple SLI won't work here, although SLI plus two more cards could) I would love to work with you! And I am not interested in money.

As for the bay converter, yes it exists http://silverstonetek.com/product.php?pid=690&area=en cable management is possible but certainly challenging. Delock and Silverstone both have interesting 90 degrees data cables in all directions which makes this possible ... at least I think. (Although by now I came to the conclusion that I probably won't be able to use this, oh well.)

Not sure there are any spots open for design consultants, but much of what goes into our case designs starts with the feedback we receive right here in the forums. I'm definitely on board with the idea of a super compact ATX case though, and if the widespread popularity of the new Define C is any indication, I think quite a few others might be too. Current the Node 605 is probably the closest to what you're describing. It's a full ATX case with the size and shape of a home theater receiver at 164mm high, and it also happens to support graphics cards up to 11.4"

That's a super nice case! I will try to Sketchup my idea and solicit feedback on the forum. My only problem with the Node 605 (and most other smaller ATX cases) is they don't support 120mm fans in the back. And yes, it is possible to squeeze that into a 4U case. Supermicro did it, I have a different idea which is perhaps simpler and cheaper to manufacture.