MrM3kon,
The limitations of the number of SAS drives is related to the particular controller. The LSI 9260-8i can connect up to 128 SAS devices, having 8 ports, but the the onboard z800 controller must have only one SAS port that supports the five drives. That is, there would an SAS port that would have up to five cables on the one connector.
That four drive 5.35" Icy Dock hot swap bay adapter appears to a very efficient way to increase the number of drives.
Cheers,
BambiBoomZ