Dear Jer,
I'm sure the same formula that determines the first break also determines the second break, so long as the surface is basically the same "flat but tilted" contour with the same green speed and delivery speed of the ball at the end of the putt. I'll have to dig back into Templeton's Vector Putting and see exactly how he would handle that, and I'll get back to you.
But the specific question you ask has a simpler answer: no two foot putt on any contour and green speed usually faced presents enough break to cause an aim spot outside the hole, and aiming just a wee bit on the high side of the center line of the cup is about all you need, so (as the coach in Happy Gilmore says): "Just tap it in, just tap tap tap it in." When the putt is inside the leather, just smooth it straight in with a slight aiming bias to the high side.
The way I personally handle this without a formula is to see the shape of the comeback curve once it crosses the fall-line to its final resting position; pretend this curve is hinged at the ball; reorient the fall-line end of this curve by "pushing down on the fall-line end as one might push down a toilet commode flush handle until the far end of the handle / comeback curve aims into the heart of the cup; look back at the ball end and see the start-line as the tangent line to the curve right at the ball; extend this tangent line back to the fall-line; use that intersection spot on the fall-line as my target for the start-line and the touch; tap it in with a smooth stroke.
Cheers!
Geoff Mangum
Putting Coach and Theorist
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