Jdoug, I just ordered the Gecko also. And I have been doing some reading on it and I am pretty sure the 40 amp will be just fine, especially with the 3200kv set up and the 28 mm prop. I ordered mine with the Race 440 and a 31mm prop. They said it will pull 25 to 30 amps with that set up. But I know that brushless pulls less amps.
I can't wait to get it. My first challenge will be to mount the servo. Not sure how yet, but once I get to look inside the boat it shouldn't be too hard.