If you launch this sandbox make sure to start and then quicksave right at the beginning, second go into translation mode, and then press "W" Notice how quickly the lander will shoot up into the air.
Now reload the quicksave and test again with the pixie engine (press space a few times, I messed up the staging)
Notes: The Pixie engine is only at 50% Consumption, but the RCS still should not be able to out perform a pixie so easily!
@AndrewGarrison looks like it is time to stack some thrusters!