What factors affect the magnitude of advancement for bimax?

[4040gate]

I'm planning to get it within the next year hopefully what factors affect the degree of advancement so I don't end up disappointed with the final result

 

[2-CB]

I'm planning to get it within the next year hopefully what factors affect the degree of advancement so I don't end up disappointed with the final result

Mostly whether it's for medical/functional reasons or solely aesthetic- your surgeon will always know best though