Rotterdam ships

I realized today that the Rotterdam ship Zeekalf was probably the same size as the ship Dolfijn (or Dolphijn, in the archaic way of spelling the name). The Zeekalf is listed with different Rotterdam last figures, but when it is 180 Rotterdam lasts, that is about the same as the Dolfijn, built in 1631 or 1632. An ship size in Amsterdam lasts is about 1.3 times the number of Rotterdam lasts. For example, the small frigates Overijssel, Utrecht, and Gelderland, listed in Vreugdenhil as 100ft x 23ft x 8ft are said to be 90 Rotterdam lasts. Of course, those dimensions are in Maas feet of 12 inches (about 308mm). An Amsterdam foot is about 283mm and is divided into 11 inches of about the same size inch as those in the Maas foot. You can find my example of how to do the conversion at Kentishknock.com. I also list what seems to be the correct dimensions for the Dolfijn. My working hypothesis is that about the same dimensions were used for certain sizes of ships in lasts over an extended period of time. That may be wrong, but I have not found a way to check the hypothesis yet, as I lack Rotterdam ship dimensions for the 1620's and earlier.