I have the 4120/14 and use an APC 13 X 8E running on 4 cells. It pulls 55A. and I see 700W. on my AstroFlight Whattmeter.

The APC "E" series are very good props...much better for electric motors than props designed for glow engines because they are thinner (don't have to be over-designed to handle the pounding stresses of the power impulses of a piston engine, among other things )
They are much more efficient too, because the thinner blades cause less drag, and allow the motor's power to be translated into thrust, rather than heat.

Just curious...why do you think they might not hold together?
They are rather light looking ...thin blades, and less resistant to breakage if you have a ground strike.