The A6M5b will dive quite safely in AH, which surprised me. In another sim, the wings fall off at quite a low speed. But in AH, the plane reaches terminal velocity before structural failure occurs.
So I dug out some books, and I found some info in Robert Mikesh's "Zero: Japan's Legendary Fighter".
(Mitsubishi) won approval to use a feed block of their own design and to combine their design with thicker outer wing panels for an increase in maximum diving speed to 400kt. The thicker wing skin panels made the new weight go up by about 33lb and the maximum level speed down by about 3kt compared to the original Model 52.
For those of you scoring at home, 400 knots is 460 mph. The convention for such limits is to express them in IAS. This is not as high as most of the Allied and German planes, but still pretty high.
So don't be surprised if a diving Zeke does not shed his wings instantly!
P.S. The feed block reference concerns a modification to the 20 mm wing cannon which allowed extra ammunition to be carried.
[This message has been edited by funked (edited 09-06-2000).]