2x Force 3 60GB in Raid - different FW revs OK?

I have 2 force 3 SSD's that I'd like to run in a Raid-1 configuration. One drive is FW 1.3.3 and the other is 5.02 - is this OK, or should I upgrade both to 5.0.3?

Host OS is Ubuntu, array will be either mdadm, or hardware-based in a 2x2.5" enclosure with built-in Raid 1 (Kingwin HDCV-2 or equivalent IcyDock product).

Thanks in advance!