The small Rotterdam ship Neptunis, in service in 1629

In 1628 and 1629, Joris Gijsbrecht van Heerd commanded the small Rotterdam vessel Neptunis. The Neptunis as a small vessel of 30 lasts. She carried 8 guns and had a crew of46 men. In 1629, the Neptunis carried an armament consisting of 2-8pdr and 6-3pdr guns. A vessel of 30 lasts could be as small as 65ft x 16ft x 6ft. One question is if this is a different vessel from the Rotterdam ship Neptunis (40 lasts) commanded by Daniel Climmer Goeren in 1628. That was said to be a vessel of 40 lasts, but the last figure is very elastic and often just an estimate. To make things even more interesting, there was a Rotterdam ship Neptunis built in 1623 that was commanded by Cornelis Arentszoon de Jonge in 1629. This was a vessel of 30 lasts carrying 6-4pdr, 2-2.5pdr, and 10-steenstukken with 20 chambers. There was another, much larger Rotterdam ship named Neptunis that was built in 1623 and which was of 170 lasts. To throw even more mud into the soup, Sebastian de Munnick commanded a Rotterdam vessel named Neptunis in 1628 which was just 28 lasts. The complete list of old ships named Neptunis which belonged to the Admiralty of the Maze or Rotterdam must include the Neptunis built in 1614. This was commanded by Adriaan Engelen Silvergieter in 1629. This was a ship of 140 lasts that carried the following guns:

2-chambered 24pdr, 2-12pdr, 2-chambered 12pdr, 
2-5pdr drakes, 13-4pdr, and 6-steenstukken

As Prof. Jan Glete says, steenstukken in this period were probably swivel guns, not actually throwing stone shot, as their name might imply. What killed stone shot was the cost of manufacture, more than any other factor.