Sounds like a bad idea to me; I always use sugar to prime my cornies, but use CO2 to seal the keg initially.
However.... if the tap was below the level of the bottom of the dip tube, wouldn't it syphon out, assuming there was enough CO2 pressure to replace the liquid volume?
However.... if the tap was below the level of the bottom of the dip tube, wouldn't it syphon out, assuming there was enough CO2 pressure to replace the liquid volume?