And then we crawled through just about every reference there was about Japanese ship construction;
Heal, S.C. 2003. Ugly Ducklings: Japan's WWII Liberty Type Standard Ships. Naval Institute Press. IBSN 1-59114-999-X;
Parillo, Mark P. 1993. The Japanese Merchant Marine in World War II. Naval Institute Press. ISBN 1-55750-677-9;
http://pwencycl.kgbudge.com/; that depends on the above;
and my favorite;
http://homepage3.nifty.com/jpnships/; This one is Fumio Nagasawa's site. In Japanese, but with some Google translator help, you should be able to find what you need.
And then you get all this.
But, as you can see, all of the Std/Kiso E types were way less than 1000 GRT. Nontheless, I would say that many, if not most (>50%) were included in game. Some of the 'merchie' E types went right off to PB duty, and are included in game as their PB penant numbers.
Mention all this because I don't think there's 700-800 missing ships, not unless they are 150' tuna boats. Missing 20 or 30, of course, but we hammered this very, very hard and I would be quite disappointed at an error of such magnitude.