Some time ago Julian posted a rather poor (not your fault Julian) copy of a document showing how to measure cylinder head thickness. In the latest edition of Triumph World someone has sent in a better copy of this document which has been enhanced and printed. I have scanned this document and uploaded it here. Perhaps this can be put into the Technical Section. I can email a full resolution scan if necessary.
Minimum Head Thicknes.jpg
Minimum Head Thicknes.jpg