I agree with a J3 attack at this point. And yes, I also believe that there will likely be no ‘Pearl Harbor’ attack on the US.
The Carolines are an ideal spot to stage the IJN. I like to have the bulk of the fleet there and another group off the coast of China to support that efforts against the Brit holdings in the DEI and Kwangtung. Also, staging at Truk pretty much cuts the US off from doing anything useful to help the Brits for the first few turns as well as threatens the Aussies enough to force them to build ground troops for defense.
Given that the US will have spent only 39 or so IPCs by the time of the Japanese DoW it’s impossible for them to have anything to withstand the full weight of the IJN at Truk. That means that if they want to survive the will likely have to be back at the West Coast or someplace else out of the way. That adds another turn or so to the timeline before the US can intervene effectively to help relieve pressure in China/India.