Just had this post brought to my attention so thought I would answer some of the questions...
The M&H Signature which James made back in England, which we have here in the workshop peaks at 27mm in the edge, 73 in the spine, 27 at the highest point of the toe and 22 at the lowest point of the toe. The shoulders are only around 12mm.
The reason for drilling the holes on an angle is to get the hole deeper and create more of an air pocket, the dowels aren't driven the whole way down, they are more of a plug.
James has said the holes are about 45-50mm deep at most. So quite deep.
We simply mark the drill bit with a permanent marker, to make sure we don't go too far!
Paul.