Got up early this morning and got out to the garage straight away. Was I going to have sufficient clearance between the valves and pistons? The short answer turned out to be yes - the JE 9.5:1 pistons with the WebCam S-cams, 1mm deck height and 0.25mm shave of the sealing surface on the heads turned out alright.
One cylinder #1: the exhaust valve had 2+mm (greater than 2.5mm) of clearance from 60 degrees BTDC to 30 degrees ATDC on the overlapping stroke, and the intake valve had minimum clearance of 2.0mm to 2.25mm from 2.5 degrees ATDC to 10 degrees ATDC and 2+mm of clearance everywhere else.
Once I had the results from cylinder #1, I chose to check the intake valve clearance only on cylinder #4 from 10 degrees BTDC to 20 degrees ATDC on the overlapping stroke. The minimum clearance was 2.5mm from 5 degrees ATDC to 10 degrees ATDC and 2+mm clearance everywhere else.
Per Wayne D's 911 engine rebuilding book, the minimum clearance for intake valves is 1.5mm and for exhaust valves is 2.0mm, so my engine passed the piston to valve clearance check!
Test set up for clearance checking:
Data record sheet of piston to valve clearance:
