Managed to keep the momentum, despite various distractions. I've used a packet each of the Strelets Arab Cavalry and Seljuk Cavalry to make three cavalry units, a horse archer unit and a commander.
I decided to base the horse archers moving sideways and it's quite effective
So the basic Saracen force is now complete. I'll add various other units to it as needed, like Parthian horse archers, until I get around to adding more Saracens.