There is not exact "formula" trimming the pavilion angle to crown angles that becomes the ultimate combination.
While the diagnostic programs we use are very helpful in determining light return, the diamond has to be examined in order to determine how well the refraction is.'
Also keep in mind that the angle of LIGHT ENTRY is directly relevant to LIGHT EXIT.
When worn, the diamond will not be subjected to "fixed" - ivory tower lab standards. These standards are necessary to make accurate comparisons, but once you take the diamond into the real world the standardized light entry scenario won't apply.
In addition, diamond refract based also on the type of light its exposed to.
If you take it outside on a grey overcast day, you'll get the refraction of grey overcast, dull light. If you take it out on a bright sunny day, most diamonds will almost blind you with dispersive spectral refraction.
Regardless of which expert you pick, you should have your portential selection checked by someone who has the proper equipment and the expertise to advise you without bias about the stone.
Some consumers want the "cat's meow" of light refraction, internal symmetry and cut quality, some are willing to accept a little less, providing the price being charged is competitive and establishes and good value with POSSIBLY only a small difference
Hope this helps.
Rockdoc