We are a group of students from spain and we are trying to replicate your boat, I have to tell you, you have done an amazing work!
Well... we have made the one with the air propeller and the servo, but we are printing the two propellers version too (well, the two pieces to midify it)
But we have this: http://www.hobbyjess.es/es/product/emisora-flysky-gt2b-24ghz
Does it works?
I don't know how you did to chenge the direction giving more power to one propeller than the other... Do we need an special ESC?