Found this lanyard usage description on another forum. It looks like Tommy is by the regulations, but I neglected to draw the sliding brass loop all the way up against the right armpit which would have given more slack on the lanyard.
Cavalry Drill Regulations, 1916, Manual of the Pistol:
"When a lanyard is used the snap is attached to the butt of the pistol, the lanyard is passed over the head and the sliding loop drawn snug against the right armpit. The lanyard should then be of just such length that the arm can be extended without constraint."