Specific to your answer, I've used my Burgundy Hammer as a spare ball and one to use on drier lane conditions. The ball, which I purchased in 1995, was drilled straight-up, but I've since had a weight hole drilled to allow it to pick up a little sooner. According to a Facebook conversation I had with Bill Hall, who designed the Blue Hammer, he told me the RG on the ball (Burgundy Hammer) was 2.52 and the differential was about an .020.
You can always put some shine on a urethane ball, which would enable it to skid farther down the lane. This was a common thing done back in the day, say, with the Columbia U-Dot: dull finish (first ball), shiny finish (spare ball).