I have not seen this in any published source, but from multiple documents from the "Directies ter Equipering van Oorlogschepen, 1631-1657", we have detailed information about what ship Gerrit van Lummen commanded.
From an undated document that mirrors what was published in the First Dutch War, Vol. I for the Amstedam Directors, I first knew what ship he commanded.
His ship was the Neptunis (the archaic spelling). His lieutenant, at that time, was Jan Danielsz. van Luijck.
The dimensions for the Neptunis are:
|Height between decks:||7 feet|
(this is from a document from 12 March 1652).
The armament was 34 guns:
4-24pdr brass belonging to the State 12-12pdr 6-8pdr 6-6pdr 4-4pdr 4-3pdr (this totals 36 guns and is from a document from a document dated 8 November 1652--National Archives 1.03.02 Inv. nr. 8)