I'll echo Dave's sentiments about the 920A, i've had mine for awhile now and have used it on a variety of patterns, from THS to Shark and Kegel's Beaten Path and have found a good amount of success on all of them...
For being a high end ball, it gets through the heads very well (layout is pin over ring, about 4 1/2" from PAP for me, MB next to thumb, no weighthole) thanks to the pin placement and the pearlized cover. The strength of the ball makes sure that there is no squirt through the mids, and it definitely makes a strong, but controllable, move off the spot.
When i'm on fresher, heavier conditions, the 930T is the ball to start with, as the lanes start to open up a bit, the 920A is definitely the piece to go with
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Andrew Loose
"Technology is anything that's really cool that you don't know how it works, and if it breaks, you have to buy a new one!"