From what I have seen the Immortal Solid cover is super strong.. The differential is also super high. Drilling leverage would more than likely be way too strong and over flare for all but the lowest rev bowlers.
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16-17 mph,350 rpm,PAP 5 1/2 x 3/8up, HighGame 300 x 3, High Series 782
Book Average 215 / 205,PBA Xperience ave180