Having once been involved in motorcycle racing and, later on, inspection, the old rule about a .0.5mm overbore turned into a can of worms and was dropped. I believe it was pretty much only an SCTA rule anyway.
You had, in the motorcycle classes, an aggregate total of allowable oversize of 1cc...... In the car classes, you had a theoretical aggregate total of allowable oversize of 1 cubic inch (16.387cc)..... DON'T CONFUSE THE TWO OF THEM!....
NOW, for any car guys reading this thread, in practical application (and Stainless may remember this), in some of the car classes, the cubic inch breaks did not exactly corelate to an exact equivlent cubic centimeter size - specifically the 750cc - 45 cu. in. class ..... 45 cu. in. equals about 737.5cc - so you actually have less than .3 of a cubic inch of "grace" in that class.
One other option for testing swept volume is the use of a burrette, which, after the valve gear is deactivated, can be pumped into a cylinder with an adaptor into the spark plug hole.....once the air is expunged from the cylinder and the piston is taken to bottom dead center, a slow turn over of the engine will pump the oil back into the burrette and establish the swept volume of the cylinder being checked. The amount, when multiplied by the amount of cylinders, establishes the "as inspected" displacement of the engine it is accurate to about 1cc (or less per cylinder - and usually shows the displacement as being on the smaller side of "as measured and calculated")..... SCTA uses this option on motorcycles and smaller displacement car engines if the owner of the vehicle is okay with this procedeure.... it can be a time saver and, if you have expensive head gaskets and o-rings etc, it can save both time and money on a teardown... You do have to run the engine a bit after with a slightly hotter plug so as to burn the residual oil out of the cylinder as well....
It may be worthwhile to ask if this is also an acceptable method.