I drilled mine 1:30 Label, like the sheet (1st time), and it will go longer on the medium patterns (with my speed), but still moves when it finds the drier boards. Depending on your speed and rev rate, I would go with a 4x4 stacked, or a 3 1/2 x 2 to 2 1/2 stacked. These should give you great backend; if you want a lengthier drilling, with good backs, try the 1:30 Label.
Dave
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