Richie,
I'm interested to know why you think the O ending is better than the A ending. There are other examples of the A ending from the period. I seem to remember 'John Dory' has the A ending and a quick glance on the opposite page shows an early version of The George Aloe, both from the early 17th century if not earlier.. The A ending may simply have been fashionable in the earlier period, 16th century. I see from Child's variant notes (p137) that the 10Ac Wit and Drollery version repeats the A endings.