I perpetrated the Sneaky Karl on Dave in Game 216. On J2, I messed up his takeover of the spice islands, and ANZAC got +10 (whereas Japan lost about 12-15 income for 2 turns).
The delay in the USA entering the war makes this a shaky, fairly break even move on J2. I don’t see most Japan players waiting to take the big money until J3 anymore.
All that is needed to blow this move is to leave the troops on the transports during the interturn.