Strictly speaking, for greatest control of out-of-balance forces, the counterweights should be moved inboard touching the cheek radius, and made as thin as possible to concentrate inertia as close directly opposite (180°, at the smallest diagonal) to the pins as possible, with the OD increased as needed to get the correct mass back. Any late weight adjustments (holes, Mallory) should be limited to the shallowest correction to the inner face of the CW only.
Not practical.
This is true (and nearly impossible) even for the "inherently perfectly balanced" L6 engines as well.

Note that the Winbergs shown are directionally biased for rotation...