Are you making your own cheek irons, or buying them? If buying them, you might hold off on cutting your cheekpiecess for the trunnions, etc., as cast irons are tapered, and will definitely affect progress until you have them in hand.
I considered red oak for new cheekpieces on our 6pdr, but due to it's nature to split, decided against it, as I definitely didn't want to run the risk of damage due to recoil.