Yes, from my own experience, I think I can confirm that you could try to insert your own disks.
Please note ALL the words, especially "could try to"
And, as I wrote before, you'll not get FTS's warranty for any later damage or unclear problem reasons, of course. Any future issues will always be caused by these inofficial disks...
It also depends on where you got your disks from. If they run on general purpose firmwares, and can get recognized in other "stock-market" machines as well, then these will probably work.
If they come fitted with a special firmware, like e.g. FTS Eternus disks, then these will most probably NOT work.
And please be aware, just in case, that SAS controllers can actually drive SATA disks, but not vice versa.