That is where the confusion comes from. People incorrectly assume that statement means 50% bore Diambut a good rule to follow is to make the cylinder head's squish band about 50-percent of the cylinder bore area.
50% bore AREA is not 50% Bore DIAMETER
You Previously posted math for 72mm Bore 277
"With your 277F, 72mm Bore, Head Chamber is usually 1mm Over-Size, but measure it, so 73mm at 50% = 36.5mm/2 = 18.25mm is the Squish Band Width."
Equation for Area of a Circle - Area = Pi x R squared
73mm = 4185 square mm
36.5mm= 1046 square mm
4185-1046= 3139 = 75% squish band area NOT 50%
Correct math for 50% AREA on 73MM bore = approx.10.7mm band
NOT 18.25mm squish band as you previously calculated based on diameter only