MrM3kron,
I look about for a solution for a z620:
ICY DOCK EZConvert PRO MB982SP-1S
General 2.5" SSD to 3.5" SATA Hard Disk Drive HDD Adapter CADDY TRAY CAGE Hot Swap Plug
If there is a 4 drive-2.5" to 5.25" bay adapter that is reasonably priced, that would be the thing as that would leave all the usual 3.5 bays still available. Do you have a link to that unit?
What RAID controller are you using?
In the end I bought an HP Z Turbo Drive MM.2 256GB and that freed up a drive bay so all three are available. A the moment I only have a single 1TB (Seagate Constellation ES.3). Someday: Z Turbo + SSD scratch disc on SATA 0 + RAID 1 of mech'l HDDs in the other two. That will run off an LSI 9620 or similar.
Cheers,
BamibBoomZ