Accelerating Carriers...when?

[Coach Z]

When is a good time for a Japanese player to begin accelerating his late war carriers?
In one game I am in July of 1942 and have captured most of Northern China and NW Oz...the battle for Darwin rages. The KB is still intact although 3 Carriers are in various states of repair (each around 40 system damaged) and 3 US carriers have been sunk (plus the Formidable & Long Island are also gone).
In addition he has lost 4 US & 1 RN battleships the largest ship I have lost has been a heavy cruiser ( Kinugasa & Furutaka).

I am thinking of accelerating the UNRYU Class Carriers. I feel that will be more cost effective then the TAIHO...even though shes a much better ship, the durability factors 115 vs 68, make me want to accelerate the UNRYU's first.
So when should I start? How many?

FYI
I have 114,000 HI and nearly 10,000 Naval Shipping points (with a surplus of 432 per turn).

[Shark7]

Personally what do is to turn off Shinano, leave Taiho on normal and with Shinano off I start accelerating Junyo/Hiyo. Once those two are done I accelerate 2-3 unryu's until Yamato finishes, then more of the Unryu's with the points I've now freed up. Turn Shinano back on at normal when you feel as if you have enough free points per turn to do so.

Other's probably do it differently, but I like to get the Junyo/Hiyo out as early as possible, cause having 2 extra flight decks early in the war when I can actually use them helps a ton. And Shinano is a resource pit of limited value, Taiho is just to big to be worth accelerating in my book, espeically when I can build 2 unryu's for the same cost, 3 in the case of shinano.

[Coach Z]

Ok I already have the Junyo & Hiyo, and yes I turned the Shinano off!