Looks pretty good. The one I wonder about quite often is whether there were any melanistic Cossacks, possibly absconding slaves of the Turks. Runaway serfs and slaves were welcome to join if they learned Ukrainian and professed themselves Orthodox believers, and there are records of Cossacks from very far afield (Italians, Spaniards, Englishmen). Was there a colour bar, or are we painting our shaven-headed axemen too uniformly in their skin tones?