Propellers formed

Using a Stanley knife and a file I recently took to some 4.5" model aeroplane propellers to make them more suitable for ROV work. Because they density of water is much high than that of air long propellers would create significant drag on the motors which according the ROV boards I have been frequenting at least will cause them to die prematurely.
2cm was removed from each blade of the propellers - turning them into 2.9" or 7.4cm propellers.
Minor differences in the thrust produced by each propeller will be handled in software - where PID stabilization algorithms - coupled with a gyro should be able to even out the thrust produced by each propeller - individually driving each one through a PWM controlled H-Bridge.