I don't know a lot about Girolamo Pennacchi (although Carlo Promis might). According to Duffy, Henry VIII hired him to conduct his siege of Boulogne in 1544. He was apparently paid the almighty sum of 5000 pounds per year and was given a house. This amount seems almost unbelievable. Consider that John Rogers was being paid 50 pounds per year at approximately the same time. Regardless, Pennacchi's success was short-lived; he was cut in two by a cannonball during the siege.
According to the Timeline of Art History, he was also known as Girolamo da Treviso the younger
and worked as a painter of some minor repute.
There may be more details on Pennacchi but I don't want to bother looking. The Grove Dictionary of Art may be a good start. Carlo Promis will likely have some details. And it seems that Duffy's research is based on Oman's classic "Art of War in the 16th Century."
UPDATE: I've crunched the salary numbers. John Rogers salary was the equivalent of about 3.9x the salary of building craftsmen in London. In other measures, it would equal over 100,000 eggs or 68,000 liters of beer.