Rackmount WS case bigger than 4U?

Update: Rezzing this post. Comment below.

I can't seem to find any 5U+ rackmount cases that fit a typical system config. Everything I can find that's 5U and up is the "double stacked" style with redundant power supplies or a million drive bays. I submitted an inquiry to these guys, but I don't think they'll be into designing a custom case so I can buy just one or two. I'm already using the system (studio workstation) in a 4U, but the cooling isn't so hot (cool, even), so I'd like something where I can fit a taller heatsink (currently using a Noctua NH-C14) and have better intake.

My current case is this bastard. I've replaced all the fans with Noctua PWM fans, so I'm really hoping for some input on the case situation. Wendell or Qain, you guys wouldn't be interested in constructing a custom 5U for me, would you? ;) I'd shell out for it.

On a related note, has anyone heard of a case being 3d printed? Just curious if it's a thing.

Since such cases really don't seem to exist, here's my stupid idea:
Take two 4U rackmount cases, take the top off one of them and the bottom and motherboard tray out of the other, and solder or glue them together such that you get one giant case (or don't glue/solder, but be wary of dust).
You could do a similar thing by taking a metal saw to a 1U or 2U case as well I'm guessing.

Does it need to be rack mounted? if not get a rack drawer and put a tower laying on its side on the drawer. If you absolutely need a rack mount get a liquid cooled heatsink there is usually enough room in there to put a radiator. I was going to make this a project this summer for my home server rack.

I am guessing this is for a home environment so you want silence, Maybe look into better rack cooling...

Ok... I just found this old IBM 5U on eBay:

Does anyone know if or think I could jam a CEB/ATX mobo inside one of these cases if I take all the old stuff out?

Here's a similar mobo on Amazon that's from a (slightly?) different model:

It's difficult to tell as it doesn't have measurements listed, but it looks similar to ATX. Hoping someone here has seen this in the wild.

Here's another:

IBM Netfinity 5000 System Board 61H0504 https://www.amazon.com/dp/B00BCNDUH4/ref=cm_sw_r_cp_api_YRFpyb4G9D6BA

20"x14"x6" sounds far too big to match that picture, but I suppose I can give it a go with the case and find out... Thoughts, anyone?

The only thing which comes to mind is ye olden SunFire servers. They were huge, but I don't think you can find them anywhere except city dumps nowadays.