You do need to do some mods inside. Remove all the HDD trays, and make a new internal support for the cards (the default support you see in the pictures wont do).
Also, by removing the HDD trays, you lose support to screw the Frontal fans and you also lose support for the front I/O panel (usb, power and reset) so you need to put it somewhere else.
Well yes, there are plenty of "similar" cases on the market, but the magic of the RSV-L4000(4500) is that it seems to work without any major modifications.
Did you try modding the Unika case?
I've did one frankenmod of a CHIEFTEC UNC - 410F B-OP, but it took too much time and is not something you would do on a larger deployment.
Yes I am making a new bar to screw in the cards. The default one is too thick and the holes dont match the cards. Other than that, I removed every tray to better fit the cards. Its perfect. You just need to find a way to secure the frontal Fans and fontal I/O since without the trays there is no place to screw them in.
Heres a picture from someone in this forum who did the same: