Nope - you need the entire stroke change as reduction in the journal.
This error has resulted in mis-calculating the displacement, deck height, compression distance and static compression ratio many, many times over the last 75 years.
However, unlike certain other errors, it results in conservative but disappointing dimensions (smaller displacement, lower deck height, not enough compression distance, and lower static CR) that are not inherently destructive.
Frequently the motor is run like this, and because it does not fail the owner passes along the mis-understood experience as fact and wisdom.
When you reduce the diameter eccentrically, the centerline of the journal (the point of rotation, and the offset) only moves 50% of the diametric change (less any minor correction).
The only time the movement is 1/2 the stroke change is when the journal diameter is preserved by welding.
