what is... ?
ROG = Rise off ground
A stock 27 turn motor might fly the plane direct drive with about an 8 x 4 prop on 7 cells. BTW a stock car motor is actually slightly lighter than the recommended Speed 600.
Generally geared works best but that motor is not really powerful enough to use with a high ratio box like the one you have. You'd be much better with a lower turn motor like the Magnetic Mayhem (22 turn) or even one of the 17 or 19 turn modifieds.
But if you want to keep it simple try it first without the gearbox on 7 cells. If it doesn't fly very well you'll need to rethink.
Steve