I find it interesting that the I-400 class was developed for the sole purpose of attacking the Panama Canal, the float planes where supposed to carry bombs to destroy or damage the canal locks which would make the process of transferring ships from the Atlantic Fleet to the Pacific Fleet or vice versa take more time, although an attack like the would of most likely failed as the defenses made the Panama Canal one of the most heavily defended US controlled territory. How much that would of effected the war I can't say since where major shipyards on the West Coast and ship production would probably outweigh any damage done to the Panama Canal itself.
@Mr Quatro The last remaining Seiran float plane was restored at the United States National Air and Space Museum in Washington, DC.
http://ahoy.tk-jk.net/macslog/Japane...eI-401fou.html