I have never made the 7-10, but I have made the 8-10 by shooting at the 10 and bouncing it across the deck (I am right handed). As to why I shoot the 10 pin, it is because of two things.
1) I am very accurate/consistent when shooting 10 pins.
2) Since I usually try to increase the speed of the ball when I throw for the 7-10, I tend to have a higher backswing. This means that my shoulders open during my approach/swing. That said, it is easier to feed the ball to the right where the 10 pin is, than it is to keep your shoulders closed and shoot the 7 pin cross-lane when my backswing is that high.
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I can't believe I ate the whole thing......