The BriStar can be tempermental from my one experience, they have different mixes for different temp ranges. I actually had to reorder beacuase of a cold snap. I can't speak for the other brands, I have only used BriStar the one time. Drilling holes versus chipping? The only reason I used BriStar was that I couldn't cause heavy vibrations beacause the room beneath us was a lab running 24/7. If vibration isn't an issue I would try chipping or sawcutting a relief line and then chipping.