Here is a useful formula to calculate how spin-friendly a frame is based on its weight distribution and stiffness. The index doubles as an arm-safety index, and it is much more accurate than the index used in racquetresearch.com (but derived similarly). Spin Index = 10000*[ I - M(R-10)^2 + M(R-4)^2]/[3kM(R-4)^2] I = swingweight about 10-cm axis in kg-cm^2. M = mass in kg. R = distance from butt to balance in cm. k = RDC stiffness rating Here are some guidelines for what these spin index values mean: 85-90: excellent spin - excellent arm safety. 80-85: decent spin - good arm safety. 75-80: so-so spin - so-so arm safety. 70-75: poor spin - tough on the elbow. These values give a measure of the relative "bite" on the ball for a given swingpath, as well as the relative dwell time. In general, any frame can be made more spin-friendly and more elbow-safe without sacrificing performance by polarizing the weight distribution (adding weight to both the tip and the butt).