Comparing with the Mair illustrations, his fencers appear to use a bit wider grip, which ought to make it easier to control the whole weapon. Still with a full weight flail, I bet you would have to work pretty dynamically with the grip.
An interesting aspect of the illustrations, that become apparent with the flails, is that the fencers are posing and are not caught with a snapshot of actual fighting, at least judging from the hanging flail heads. I have to look into these when I get back to my own computer.
