What is the actual utility of something like The Spy? I know polyester balls with big cores have been made in the past but they've never really been very popular around here.
Does adding the core allow these kinds of balls to carry through the pins? I have a hard time imagining any kind of polyester cover picking up enough to provide consistent motion. Unless the lanes are absolute toast, but I'm not sure I would want to carry around that kind of break-glass-in-case-of-emergency option for those few odd nights or long-form tournaments.