There were tests run once that showed that bats with a very light hint of curly did not show a significant drop in strength. BUT... those were some very light "HINT" of curl. I too would not recommend to make bats with STRONG curly figure.
They Should be considered BLEMS OR DEFECTS. Straight grain Maple with a good ink dot rating only should be used for games. Chose a bat with a long taper and a slightly thicker handle and a heavier length to weight ratio than -3 for the best overall durability.
Taper refers to the barrel to handle transition. In other words a C243 would be a fast taper into the handle because the barrel is long and leaves for a short transition into the handle. A C271 is a long taper because the barrel transition to the handle is very slow and gradual.