You can leave SZ 6 relatively undefended. The destroyer block between hawaii/japan goes without saying, and buys you one round every game
Just for clarity, you mean a single destroyer in SZ 16?
What is the typical US response to this? Do you find that it gets removed every turn (by air from Hawaii) and has to be replaced (so basically a sink of 8 IPC per turn)? Or is it typically ignored?