Keep the tail rope from the cleat to the fish as short as practical. Put two tail ropes on the mako and leave the rod and reel and fly gaff attached until you think you have it under control. Makos can go into a coma and rebound several hours later. If you are dragging the mako around backwards to drown it while it is in this coma state your in for a big surprise when it comes alive hours later. To avoid someone getting bitten in the cockpit, try to get a bucket to fit over the makos head and tie the bucket handle to the tail.
Many fishermen use a shotgun blast straight down on top of the head between the eyes to kill a mako.
Personally I don't use that method, I figure a loaded gun in rolling seas with a wet deck is just another hazard, so I put up with the sometimes violent resurrections. Anticipate this and tie them down well. Once you have caught a big mako you will always be looking into the water for another. Very tightly in rough water. That way when the pull comes from the shark the balloon will come free off the line. .