Change from X-Raid2 to RAID0? [Noob Warning]

I don't recommend a single 5 TB volume. One 2 TB volume and a second 3 TB volume is much more robust. With a single volume, any disk failure loses all your data. With two volume, you only lose the data on the failed disk. You'd access the shares the same way (the number of volumes generally only effects admin functions). The main impact is that you have to balance the storage between the two disks manually (occasionally moving shares around perhaps).

If you want 2 volumes (as I suggest), then I'd do the reset with only one disk in place, choosing flexraid, and then raid 0. After it rebuilds, you can hot-insert the second, and manually create the second volume.