"I really want to know how well documented those 'huge junks' are."
Roxana:
Yes, that would be useful.

Googling around, I found this:

AHA Presidential Addresses
Voyages
By Frederic Wakeman, Jr.,
President of the Association, 1992

Presidential Address delivered at the American Historical association annual meeting in Washington, D.C., on December 28, 1992.American Historical Review 98:1 (February 1993): 1–17.

[www.historians.org]

It is referenced, which may lead somewhere interesting.

I found it by following references to these two:

i. "...rudder-post believed to be from one of the giant warships. Excavated from the mud in a backwater of the one of the Ming naval shipyards at Nanking, the rudder-post is 36.2 feet long and 1.25 feet in diameter. Using these measurements, naval architects estimate that the rudder attached to the post was nearly half its length in height and breadth, or 452 square feet of wood. That means that thirty men could comfortably lie down on it! The ship to which such a rudder belonged would, following the rules of thumb for Chinese ship construction, be at least 400 feet long. One rudder post, as a solitary find, and possibly never fitted to a ship, does not represent a fleet. But it is a tantalizing hint of a navy of gigantic ships that outweighed, out-gunned and out-classed anything afloat in a European navy of the time."


ii. "China, Nanjing dry dock No. 6 A+ The giant rudder (42 ft high) was found here, as was much very old teak – with which local people make furniture. Dock is huge -500m x 80m. Flooded 1431 until today Contacts: Mayor of Nanjing, Professor Yinsheng Liu or Admiral Zheng Ming."

The subject seems to be surrounded by pseudohistory and pseudoarchaeology, which is not to say that there is no truth in the description of such huge junks. However, when I was reading how stone walls in Nova Scotia were evidence of Chinese colonisation via these junks, I could hear alarm bells ringing...