Did you take a look on the
Klaus site? At the bottom left is a picture of the holes doing just a little more than only "shine trough".... Those are for the steel 103mm's...
I don't know to what size these heads are flycutted...(but would like to know
)
A couple of months ago LN Eng. talked about making the Biral 100mm like "thickwall" 103mm cylinders, so maybe that outer size of the cylinder will do good in your application too
...