>You can use 2 SSD on this unit.
I use six SSD´s in my Z440. 
Two in a HP 2.5in HDD/SSD 2-in-1 Optical Bay Bracket (K4T74AA), one in a 2,5´ to 3,5´adapter in the disc bay and two loose ones in the top of the chassi. (And one 7200 rpm disc in the second disc bay.)
